"What do you expect the metagame for this event to be" and "what decks do you have to beat" are not the same question.
My matchups on day 1 of Grand Prix Kansas City (Modern format):
U/W/R Control, B/W Tokens, G/W Auras, U/W/R Geist, U/W/R Control, Tron
My matchups on day 2 of Grand Prix Kansas City:
U/R Twin, Tron, U/W/R Twin, Melira Pod, Melira Pod, Twin, Living End
The Top 8 of Grand Prix Kansas City:
Anyone else catch that?
Day 1: 4 fair decks, 2 less fair but not busted decks
Day 2: 1 less fair but not busted deck, 3 hybrid combo decks, 3 combo decks
Top 8: 4 combo decks, 2 hybrid combo decks, 1 less fair but not busted deck, 1 fair deck
These results are not because of a small sampling size either. The Top 16 didn't look much different, and neither did my view of adjacent tables throughout the event.
Big Giant Red Flag Note: Metagames are not stable under most circumstances. The levels of a format shift drastically from week to week, sometimes faster online. In a format where there aren't a lot of events (Modern at times) or where external factors prevent people from adapting on a regular basis (Legacy), this might not hold, but otherwise failing to keep up to date means cycling down levels and falling behind the times.
You know those decks that everyone plays but you have no idea what they see in them? They are the decks that were good last month but became the targets to beat or that just look good on paper and attract a lot of people because that's what they want to be good. That's a level -1 deck.
Sometimes by sheer numbers a level -1 deck is a level 0 deck and is worth caring about. Or it might have just enough steam left in it to be able to keep itself in the event towards the middle rounds but not much further.
Don't get trapped into playing these decks. Of course, that's easier said than done. The usual always-repeated advice applies here. Play lots of things, try different configurations, do your homework, eat your vegetables, etc.
Ask anyone in the event "what do you expect to play against most?" This (to an extent) is the level 0 metagame. Sometimes it's a single deck; sometimes it's a few. Regardless, showing up to an event not prepared to face off against these decks is just straight-up wrong.
The majority of rounds are won and lost on the level 0 metagame. Each round of an event is effectively a metagame filter, and it takes a while for enough orders of filtering to build up to eliminate the noise. If the entire tournament were people playing "real" decks and every match was 100% deck and skill related this might be different, but there is a random element to Magic and a certain percentage of the field shows up playing decks that either are strictly worse versions of other decks or simply can't win.
Large PTQs have enough rounds to filter past a level 0 metagame but only towards the very end. Even then with the Top 8 being single elimination it's very possible for a less optimal deck to advance through to the finals. Pro Tours are the right number of rounds, but the Draft portion in the middle shuffles the event (though now that it's one draft in the middle instead of two this shuffling might be less relevant). Even at a Grand Prix you don't get past the level 0 metagame until day 2.
Don't let the name here fool you. There isn't always a deck that is better than the level 0 option. Jund in Standard is currently a level 0 deck. Jund in Modern was a level 0 deck pre-Bloodbraid Elf ban. Jund in Alara-Zendikar Standard was a level 0 deck. Sometimes the obvious deck is obvious because it's the best.
In Modern, the level 0 metagame is almost entirely one deck: U/W/R. Whether it's the Wafo-Tapa style list that everyone played at Worlds or the Larry Swasey Geist list or even a pre-Seattle Delver list. Besides the obvious "this won the last big event" logic, this diversity is a big part of why U/W/R is so prevalent. Play style—or more accurately play patterns an individual player is familiar with or enjoys—are a huge part of what people play, and U/W/R has a wide range of appeal. Like feeling in control and that your decisions matter? U/W/R! Like Geisting people and burning them out? U/W/R! Like having a lot of powerful board options for that matchup you have no desire to lose to? U/W/R!
Another reason U/W/R is a level 0 deck in Modern is accessibility. In terms of rares, the Geist lists are three Vendilion Cliques, four Celestial Colonnades, and fetchlands away from a Standard deck. While this may not sound like a small amount given the going rates on these cards, these are cards a lot of people incidentally own due to old Standard formats or Legacy. These cards are also "format staples," branching into more archetypes than something like Karn Liberated.
Besides U/W/R, the closest thing to a level 0 deck in Modern is Pod, but that deck's metagame presence has been slipping a lot online. Jund pops up a decent amount, but see the point about accessibility above. Four Dark Confidants, four Thoughtseizes, four Tarmogoyfs, four Liliana of the Veils is not that, and even if U/W/R came close on Magic Online, people are just more adverse to buying four 60-ticket Tarmogoyfs as opposed to a bunch of 10-30 ticket Cryptic Commands, Celestial Colonnades, and Vendilion Cliques. Don't ask me why; they just are.
What does U/W/R exclude from the metagame? Well, in my experience I don't want to get into a matchup against it with Affinity. Between Electrolyze, Spell Snare, and Snapcaster Mage, getting anything to hit them is a pain. Beyond that I've actually felt fine playing literally anything against them. Even Burn was enough against the Think Twice lists, which tended to do a lot of nothing.
Besides U/W/R, what else do we have to handle? Well, G/W Auras is another prime suspect since Reid Duke finished second at the World Championship with it, but I'm wary because of how the finals played out. People on the popular deck know how to beat it and are also aware it is a threat. The deck does not stand up very well to hate and (spoiler) has other issues with the relevant metagame.
What about Jund or B/G? I'm unsure. Not accessible and hasn't put up real-world numbers lately, but at the same time Jund is Jund. At the least, a lot of what beats U/W/R tends to hold up against Jund. Be aware Tarmogoyf and Liliana of the Veil are cards; that's all I've got.
This applies less to real-life Standard events, but on Magic Online and in Eternal formats there are often a few "default" decks that people play because they are the easiest things to build. The classic example is Legacy Burn. The deck costs basically nothing to build, so people who just want to play in the event show up and run it. Other examples of this in Legacy are Dredge, Elves (up until the recent move to three or four Gaea's Cradles), and to some extent Lion's Eye Diamond decks.
The thing is that not every default deck is created equal. Some of them are just straight-up bad. Some of them are incidentally good metagame calls. Most of the time, it's safe to ignore most of the bad default decks under the assumption that they will lose round 1 and you won. The exception to this is if the metagame is oversaturated with them, such as Mono-Red Aggro in a lot of Magic Online formats.
The default decks you care about are the ones that are incidentally good. There are metagames where Burn is very well positioned in Legacy. In Modern, Tron is often both a solid choice and something that people can easily assemble. In the middle of last PTQ season, G/W Auras filled a similar role.
Simply put, unless you have insane margins against the rest of the field, don't play something that loses to the relevant default decks. You don't have to demolish them, but showing up with no plan to beat them is not a good idea.
Again, this only applies to the decks in this category that are capable of winning against the level 0 decks. The others are safe to ignore. In current Modern, that means you can likely ignore Merfolk since it folds to Supreme Verdict and Snapcaster Mage but should care about Tron. Martyr is another one of these decks (except when you're playing Burn and seem to run into it in winner's brackets).
So you need to beat the level 0 decks (U/W/R) and manage the relevant default decks (Tron). What does that?
(Let's ignore the fact that I think Pod can be built to beat basically anything. And by fact I may mean bias.)
Now you see one reason I don't like G/W Auras. It fails test two. The Tron matchup in my experience is not great. You can kill them early, but Oblivion Stone comes down and activates first most of the time.
Under these assumptions, the Mono-Green Tron deck that one specific player (I don't remember your user name, sorry) jams all the time is awesome. It's Tron, so it beats U/W/R barring them having a million-card board plan, and it beats the mirrors by cutting random interactive nonsense for cyclers (Mishra's Bauble, Gitaxian Probe) and Mindslavers. Are you willing to sacrifice the edge against other decks to attack "the meta?" Well, that comes down to how much of the event you expect to be the metagame. Playing normal Tron is perfectly fine if you feel like the metagame is too open to go that far with your deck choice.
Looking at less narrow decks, Scapeshift also seems reasonable. U/W/R has a habit of doing a lot of nothing, and Scapeshift's big issue is that it struggles to keep up with decks that do things. Against something like U/W/R, it's much easier to set up for your one big turn and resolve a lethal Scapeshift through countermagic. As much as I hate the deck, now might be a good time play eight-card combos.
We've established our level 0 (U/W/R, potentially other midrangey decks) and our level 1 (big mana).
Why do we need to go to level 2?
To answer part of this, what event are we preparing for? In this case, the answer is the MOCS coming up this weekend. Sorry for those looking ahead to Grand Prix Detroit, but that metagame won't be ready for another couple weeks. From above, even at a Grand Prix you won't arrive at a level 1 metagame until the late rounds. In a MOCS, which is seven or eight rounds of Swiss plus Top 8, there's a real chance that it won't ever form.
The incentive lies in the prize structure. First place gets everything; second place gets a pat on the back and told to try again next month.
Maximizing your odds of a Top 8 might be the best way to ensure victory, but at the same time there is a real chance that going a level deeper is a better plan. A loss of some percentage to make the playoff rounds compared to an increased percentage of winning once you are there is a fair trade off if your goal is first place and first place alone.
You can now see why the Grand Prix Kansas City Top 8 and day 2 was like it was. Prior to that tournament a similar metagame scenario existed, albeit without the immediate result based incentive to play U/W/R.
So what's level 2? Various non-interactive decks that are faster than the big mana decks. Twin, Living End, and even Burn put up great numbers against Scapeshift and Tron while still being able to fight against U/W/R. Storm doesn't hold up quite as well if Scapeshift is involved and Remands start getting thrown around, but at the same time it enjoys the fact Jund is less of the metagame now that Abrupt Decay is a big issue for it.
If we want to go a level deeper, we can also see why the Affinity players that made day 2 at Kansas City did reasonably well. One of the strengths of Affinity is the ability to be as fast as the pure combo decks without the same weakness to counterspells. Of course, at that point you are going a level too deep and losing to the level 0 decks. Give it a week or two on that one.
The Big Takeaways
- Targeting deck choices to finish based on expected metagame is a real thing.
- The deck that wins the most Magic Online Daily Events is not always the deck that wins the most PTQs or Grand Prix. Sometimes it is, but it's very possible it isn't.
- For a Top 8 performance at one-day event, level 1 is the place to be. For a win at a one-day event or a Top 8 at a two-day event, level 1 tuned for mirrors or level 2 is where it's at. For a win at a two-day event, good luck.
- Always consider that the level 0 deck could just be the level 1 and level 2 deck and just beat everything.
- Not mentioned above, but some of this also applies to Sealed Deck. Building a deck that 4-0s a Magic Online Daily Event can be very different from trying to 8-1 a Grand Prix day 1.
The Little Takeaways
- People are overreacting to U/W/R's World Championship win. There is no reason Shadow of Doubt should have suddenly spiked in value the way it did.
- Land destruction is going way up in value. U/W/R has issues with it, as do the decks that prey on U/W/R (see: Tron).
- Affinity is one of the coolest decks in the format. Now is not the time to play Affinity.
One of the big factors in determining a level 0 metagame is publicity. Take for example Jund at Grand Prix Atlantic City. As shocking as it seems now to think Jund wasn't a big deal when the expected metagame was a bunch of Selesnya ramp decks that died to Rakdos's Return, very few people mentioned it leading up to that event. While it wasn't the big story due to Hexproof making its first showing, it quietly put two copies in the Top 8 and was set up for its run to the spotlight after Gatecrash.
I feel like one deck is in a similar spot right now in Legacy.
Maybe I missed the mention of it (besides Adrian Sullivan scooping me late last week), but this deck went 7-0-1 at the New Jersey Invitational in the hands of the eventual winner and won the Open that same weekend in the hands of Crowd Favorites Gerard Fabiano. Talk about awesome. The deck has the brutality of RUG Delver with an answer to opposing Tarmogoyfs and access to Umezawa's Jitte. Instead of Nimble Mongoose, your untargetable guy is Geist of Saint Traft (upgrade), and you get white sideboard cards.
This deck is the real deal. Don't ignore it.