Aggro decks are different than control decks because the main deck is a lot more streamlined. You need to maintain a curve, and the cards in your aggro deck are in your deck because they’re the best at what they do, so it’s unlikely that you will be able to upgrade anything. If there was a 1-drop that was better than the 1-drop you’re playing, you’d just be playing that instead. Their proactive nature means you often cannot sideboard in a ton of cards, which means you want to be particular about what you’re bringing in. Most of the sideboard in an aggro deck is dedicated to specific hate or to slowing your deck down a little bit—this operates under the assumption that people will have more cheap answers, and therefore you’re less likely to just run over them, so you need a plan when the game goes a bit longer.
Aggro vs. Control
In aggro versus control, keeping some semblance of a curve is paramount. You cannot make your deck too slow because, if you do, you can’t compete. What you usually do in those matchups is take out whatever interaction you have in your deck (removal, burn, pump) for threats that are hard to deal with. Planeswalkers like Gideon and Tamiyo are perfect because they are cheap enough that they won’t disrupt your curve too much, threatening enough that they have to be dealt with, and different enough that they won’t just be swept away by whatever answer your opponent has. In general, I always like to have cards that survive the sweepers (such as Languish or Kozilek’s Return) but I try to avoid cards that do nothing unless they have the sweeper (such as Eerie Interlude), and planeswalkers match this description perfectly (as do Vehicles from Kaladesh).
Here, we can see that Chris’s sideboard against control is very specific—4 Gideons, and that’s it. He wants to be able to pressure his opponent with a threat that is hard to deal with, and he knows he cannot board in a ton of cards because he has to keep a good curve and good threat density. Going too low on threats is one of the big mistakes people make when boarding against control, but this sideboard just swaps a couple of removal spells (and perhaps some expensive cards) for 4 Gideons.
Aggro vs. Aggro
In aggro versus aggro, you generally want to increase your curve a little bit and to have some late-game trumps, much like one of the options in the control mirrors. Since you’re not as limited by a curve in this particular matchup, you can take out more cards and have a bigger sideboard.
The slower the deck naturally is, the greedier you can be. If you’re playing a mono-red mirror, for example, then you can’t just board in a 6-drop because you will die before you cast it, but the Bant mirror allows you to do something like this if you want because it’s a lot more prone to board stalls.
It’s important, however, to recognize when the “increase your curve” plan is just going to fail. At PT Milwaukee earlier in the season, there was a very popular R/G Aggro deck that included the Become Immense/Temur Battle Rage combo. The great majority of the tournament decided to cut the combo post-board in the mirror (which made sense, as you’re playing versus removal) in favor of cards that are historically good in mono-red matchups, such as Thunderbreak Regent and Outpost Siege. Our conclusion was that if people were going to do that, we’d just keep the combo in and kill them immediately when they tapped out to play those cards, and it worked—all my mono-red mirror opponents just killed themselves by playing a do-nothing on turn 4 and leaving the coast clear for us to kill them with the combo. Here’s our deck:
Our sideboard against aggro is just 2 Fiery Impulses and 2 Hordeling Outbursts. We recognized that you wanted threats that were harder to deal with, but still paid our respects to the speed of the matchup. Compare that to the other Atarka Red sideboards that went 7-3 or better in the tournament:
One team (DEX Army) arrived at the same conclusion we did and played Hooting Mandrills as their mirror card, a threat that is hard to answer but that lets you keep mana up to stop their combo. The other builds, however, all played a good number of expensive cards, Outpost Siege and Thunderbreak Regent chief among them. Those cards were there in large part for the mirror, but they were actually not good in the mirror match, and I think anyone who played them was making a big mistake.
Another example is the last year’s Worlds semifinals, where Paul Rietzl played against Owen Turtenwald. Paul had a more aggressive version of Abzan, and Owen a more controlling one. In the post-boarded games, Paul tried to adopt a more controlling version himself, which is what you usually do in those matchups, but Owen’s version was so much more controlling that it was a wasted effort—Paul simply didn’t have the tools to out-control Owen. I think he would have done better to keep with his aggressive plan (keeping his Dromoka’s Commands and Anafenzas, for example) than trying to morph his deck into what basically amounted to an inferior version of his opponent’s deck.
Aggro vs. Combo
In aggro versus combo, you again want hate but you can also diversify a little bit. The difference here is that you can apply pressure, so you don’t need the hate to win the game by itself—you only need it to stall them for one or two turns so that you can win the game normally. So you can afford something like Rakdos Charm as your graveyard hate, or Negate versus generic spell combo. Manuel Menge’s Affinity deck is an example of this:
You can see that his sideboard against combo is mostly generic with 2 Thoughtseizes and 2 Spell Pierces, with the occasional Dismember, Cage and Spellskite thrown in. Those don’t win the game by themselves, but they stall the game long enough for you to kill them with your pressure, which is something that control decks cannot do.
Next up: Combo!