60 cards.

That’s usually the number we tend to associate with Constructed maindecks. But it also happens to be, more or less, the number of cards in your Sealed sideboard (assuming regular 14 card packs and 23 spells plus a nonbasic land in your deck).

That’s a huge sideboard! And for how important we know sideboards to be in Constructed and how often the public howls for sideboard guides, it is wild to think that in Limited all those 60 cards way too frequently end up in the back of the deck box to only be scrutinized once or twice during an event with a quick sift before the player shrugs and continues to shuffle up their starting 40.

If you don’t utilize these sideboard cards, it’s like only having a couple bites of your watermelon slice before throwing it out, leaving plenty of delicious meat on the edge. And often there are enough playables – or situational playables – that you sometimes can use to completely change up your strategy to line up better against your opponent.

This is the exact concept I want to cover today; the times where you want to make major changes to your deck, sometimes switch decks completely, the reasons to do this and common pitfalls. I’ve especially encountered this a lot in Modern Horizons Sealed where most pools include two or more feasible decks, so that’s the format I’ll take examples from, though I am aware that only one Modern Horizons event is left so I will make sure to make the advice more generalized for future Sealed formats.

The sideboard juke

How to become a two-trick pony


Lesser Masticore


It won’t be every Sealed pool that can support multiple decks. Sometimes there’s only one way to go with remotely enough playables, and sometimes you can build multiple functional decks but one will have a power level that is just leaps and bounds better than the other decks, so that you could never sensibly board into something different.

But it also happens quite often that you’re laying out multiple decks as you build your pool and try to weigh them against each other to see which is better and these are times where it can be really important to remember these other decks. You made the decision of which one to play based on general expectations of what you’d meet, but now that you have an actual opponent with an actual deck, that context has changed and sometimes it would mean that your other option is actually better suited.

It can be an entirely new 40 cards, sleeved up in your deck box and ready to go (maybe you just need to put in that Lesser MasticoreLesser Masticore from your main deck). It might just be turning your Red-Green deck into a Green-White one, where you just have all the white cards – plus an appropriate number of Plains and the one Twin-Silk SpiderTwin-Silk Spider you couldn’t fit into Red-Green – sleeved up behind your deck divider. Or it might even be just staying on color but altering your strategy to be more controlling or aggressive. Or even change your deck to support Stream of ThoughtStream of Thought!

No matter how many cards it is, it’s quite important that you do all this work before you start your round. While you have byes at a Grand Prix is the ideal time, but if you don’t have those, just find yourself an empty table after round 1 and build all your possible sideboard decks. Get them sleeved up and ready and use deck dividers to keep each “module” of a deck separate. By modules I mean for instance the white part of the Green-White deck. It can also be that your main deck is Black-Red, but you can also make Blue-Red and Blue-Black, so you keep all the blue cards (and the islands) that go in both decks in one pile, the blue and red cards that only go into that deck in its own pile and the same for the blue and black cards that only go into the other.

This way your sideboarding will be much more organized, easier to hide from the opponent and you’ll actually be able to execute on time and not let laziness get in the way of proper sideboarding.


Reasons to change

What you should be thinking about

Wrenn and Six from Modern Horizons

Wrenn and Six from Modern Horizons

So what are these circumstances that could cause your deck evaluation to change?

Most of the time it comes from facing a bad match-up where the opponent has lots of cards that line up well against yours. Maybe you have Wrenn and SixWrenn and Six and double Igneous ElementalIgneous Elemental but your opponent has a green deck with a bunch of big creatures and multiple Trumpeting HerdTrumpeting Herd. At that point it might be better for you to board into almost any other strategy and that mediocre ninja deck with two String of DisappearanceString of Disappearance will do just fine.

While it usually takes a bad match-up for you to switch as you generally won’t feel the need if you win game 1, I’d still urge you to consider your options. Especially if you’re familiar with how some of the common “match-ups” play out among archetypes you might have a good version of a deck that lines up particularly well, like Red-Green against a small creature deck like Red-White Slivers. Do note that this isn’t Constructed and individual cards and the way they line up can always change the texture of this, like if the red-white deck has GoatnapGoatnap and Settle Beyond RealitySettle Beyond Reality and your Red-Green deck doesn’t actually have much small creature removal but relies heavily on Murasa BehemothMurasa Behemoth.

A thing that can also come up is that you don’t have enough playables for a deck because you can’t maindeck sideboard cards, but once those cards are good, the deck actually becomes playable. This comes up often with ReprobationReprobation a card I really dislike in this format as it’s way too easy for the opponent to punish you with stuff like blink effects, ninjutsu, sacrifice and String of DisappearancesString of Disappearances so I tend not to maindeck it. This often leaves my Green-White decks dangerously low on interaction. But if I am up against Red-Green, or maybe slivers or a snow deck without blink effects, ReprobationReprobation becomes an actual good removal spell and can make your white deck better than whatever deck you were running in game 1.


Common Pitfalls

It can easily go wrong


Goblin Champion


I will have to warn you to be aware and careful when you do this. There’s a reason that we don’t see deck swaps happen in Sealed that often, and that reason isn’t just laziness.

It’s quite easy to outsmart yourself when you do this and just board into a deck that has a lower win rate in the match-up. Even if some cards line up right, usually your deck that you didn’t run for game 1 will have a much lower power level or a less functional game plan. I mean, there’s a reason you chose to go with the other deck in the first place. And if the difference in power level is too large, sometimes it won’t matter that the weaker deck is positioned better in theory.

One approach you can use to avoid this is what I call “the worse half”-test. Your Limited decks often have a big disparity in power between their worst and best cards and sometimes you simply don’t draw the good ones. So when you sit down between rounds, looking at your sideboard decks, take a look at the weakest cards on each spot of the curve. Would those combined make up an acceptable draw when compared to the worse half of your main deck? Probably not in a vacuum but remember these speculations when you go to sideboard. Maybe the way the match-up plays out, your main deck worse half looks even more horrible.

Also don’t forget when you consider these things that you might draw your cards off curve. Goblin ChampionGoblin Champion is a lot more embarrassing when it’s your only turn 4 play. Maybe your manabase is off and you’ll have to consider how powerful your deck is when some of its spells can’t be cast, or all your red cards are delayed by a turn because you had to Springbloom DruidSpringbloom Druid for a Mountain first.

Ideally, you’d also have enough time to combat these issues by playing some games with your sideboarded decks against friends during byes or between rounds. Don’t bother playing with your main deck, you’ll get enough games in to get a feel for that one during the tournament. This is also how you can discover if a strategy is just poorly positioned against the format in general. For example, I’ve had a couple instances of a very grindy Black-White deck with GraveshifterGraveshifter, Return from ExtinctionReturn from Extinction and EphemerateEphemerate. They might have looked good for traditional Sealed decks, but in this format, I found it hard to get my creatures into the graveyard in the first place and would often fall behind with no ability to come back. The strategy simply doesn’t work well in this format, and I now know not to board into it.


Sideboard swap in draft

Can it ever happen with a 20 card sideboard?


Murasa Behemoth


While it isn’t common, sometimes you have had such an open Draft that you end up with 35-40 playables and your deck can be built in different ways. This has come up for me with Red-Green in Modern Horizons which can be built both as an aggressive deck and as a big ramp deck based around Springbloom DruidSpringbloom Druid and Murasa BehemothMurasa Behemoth. I had a draft with enough playables to build either version, and so if I faced a match-up like Blue-Black Ninjas where my big green creatures didn’t line up well I could always board into a deck with a much lower curve of red creatures.
It can also happen if you stick to primarily a single color throughout the Draft, waffling between options for your 2nd color. Then you can end up with the ability to build, for example, either Blue-Green or Black-Green. And here the same principle applies as it does for Sealed where the context which you used to make the decision to go with one of the builds will have changed once you know your opponent’s deck.

This can also happen in Magic 2020 Draft for instance where Mono Red is a reasonable archetype sometimes splashing a couple blue cards. But if you managed to pick up a few Devout DecreeDevout Decree during the draft, it might just be better to exchange your blue splash for a white one and run those instead.


If you are going to take away one lesson from today it is to keep spending time on your Sealed pool even after you have submitted decks. Look at sideboard options, organize, play with different builds against yourself between rounds, make sure you have the basic lands ready and sleeved up, so you don’t get a slow-play warning for taking too long to sideboard. It can be done, but you can’t be lazy.



This article was written by Simon Nielsen in a media collaboration with mtgmintcard.com