Dangers of Surface-Level Sideboarding and the Importance of Opportunity Cost

Piotr Glogowski


Hello readers, I’m happy to have joined the ranks of Hareruya Pros. Some of you might know me, most likely from Magic Online or from my Twitch stream. While I stream, I frequently get questions from my viewers, and there was one thing that was bugging me for some time that I wanted to discuss.

Many players are extremely eager to bring in their sideboard answers, defaulting to that position way too often. The proverbial case of sideboarding a 《Naturalize》 effect because your opponent has targets for it.

Lantern of InsightNaturalizeEnsnaring Bridge

The most simplistic way of looking at a sideboard is a pile of cards that are good, but narrow. This is probably why a phrase that you might hear or even say yourself, is “Well, I know what to bring in this matchup, but I have no idea what to cut for those cards”. Well, this is definitely not utterly untrue, but it’s also just the tip of the iceberg, so today I want to describe as well as I can why surface-level sideboarding might not the best way to approach things when trying to maximize your winrate.

I also think surface-level sideboarding manifests itself and is easiest to spot in non-rotating formats. Archetypes have time to develop, lists are polished, players develop cohesive plans. Since Modern is my ballpark, I’m gonna provide you with examples from this format.

Importance of the Opportunity Cost

The first rule would be that post-board, you are still looking to present a cohesive, 60-card deck, with a sound overall strategy.

When trying to get better at Magic: the Gathering, a very important concept to keep in mind is opportunity cost. Every card you add to your deck has the opportunity cost of not being any other card it could have been otherwise; this somewhat overwhelming concept gets much more palatable when we move from macro-scale of general deckbuilding to the scale of just in-game sideboarding. When you think of it that way, that’s exactly what sideboarding is – it’s deckbuilding, just from a very limited pool, and against a known opponent. Essentially, every card you sideboard into your deck has an opportunity cost of not being the next best card that’s staying in your sideboard. This is, of course, an infinitely complicated puzzle, but we can go a long way by applying heuristics and utilizing our past experiences.

When you are sitting down, getting ready for game two of a Modern match, you have to be ready to answer many possible questions. Do you want to board in 《Reclamation Sage》 to kill 《Hollow One》? Is 《Leyline of Sanctity》 worth it against Ad Nauseam Combo? Should I be boarding tons of graveyard hate versus UR Gifts Storm? For sure that 《Collective Brutality》 can trade for a card in this matchup, but does it actually pull it’s weight if escalating it is ineffective?

Reclamation SageLeyline of SanctityLeyline of the VoidCollective Brutality

Well, obviously the answer to those questions is that it’s very contextual.

Games of Magic are nearly always won on amounts of relevant game pieces that players can present. In the end, if you analyze a game, the person who gets more of their cards invalidated will wind up as the loser. This can be done by going over the top and making their cards not advance the game state relevantly, straight up trading for cards and using literal two-for-ones, or stranding cards by not allowing opponents to use them effectively before the outcome of the game is decided.

This is somewhat broad and nebulous, but the point I wanted to highlight here, is the fact that cards you didn’t play before dying are essentially mulligans, leaving you with less material to play the game. That makes narrow reactive cards naturally predisposed towards having a higher opportunity cost. A 《Lava Spike》 will be cast if you have enough mana, and a creature can always just be summoned, an answer card can get stuck. All of this amounts to the old saying that there are no wrong threats, just wrong answers.

Lava SpikeTerminateGoblin GuideNegate

Catching up the Opportunity Cost with an Example: Linear and Hyperforcused Decks

What I ended up saying in a slightly convoluted way, you are still looking to present a cohesive, 60-card deck, with a sound overall strategy. The opportunity cost of sideboarding extra cards is extremely visible when you are playing a linear, hyperfocused deck. Every 《Rift Bolt》 cut from your Burn deck diminishes your average expected damage output per card drawn. Every 《Terrarion》 you remove from your 《Krark-Clan Ironworks》 (KCI) deck decreases the odds of winning the game during your combo turn.

Rift BoltTerrarion

It’s a pretty common knowledge that linear decks shouldn’t over-sideboard, and this is exactly the reason why – every card that’s not contributing towards executing the main gameplan is essentially a mulligan, unless you manage to match it up well against relevant, opposing cards. I think it’s useful to look at answers like that – they are, in a way, essentially dead cards UNTIL you manage to make a good use of them.

Narrow, single-shot answers, so essentially removal, counterspells, and the like, suffer from this the most. It is the type of card that seemingly attracts players the most. It is extremely easy to imagine your answers lining up well, at the right time, blowing your opponent out. The reality is that depending on effectiveness, efficiency, redundancy of certain type of effect, and popular play patterns in a matchup matters a lot.

KCI Decklist for Reference

A good example that kept popping up when I was streaming my KCI deck and I was running into the 《Hollow One》 matchup. My list includes a single copy of 《Galvanic Blast》 (named differently than 《Lightning Bolt》 as a low-opportunity cost hedge versus 《Meddling Mage》), and what kept happening and was one of my inspirations for this article was people kept suggesting me to board-in 《Galvanic Blast》 with the intention of killing the 《Hollow One》 itself.

Galvanic BlastHollow One

My typical plan against 《Hollow One》 would be to remove 《Engineered Explosives》, some 《Mind Stone》 and 《Terrarion》, in order to bring in 《Nature's Claim》 and 《Sai, Master Thopterist》 expecting to see 《Leyline of the Void》. This is a perfect illustration of a situation where a card in your sideboard seems to be effective on surface, but in reality it doesn’t pull its weight《Hollow One》 is covered as a secondary target for multiple 《Nature's Claim》 that I will be sideboarding in regardless, and yet 《Galvanic Blast》 still doesn’t solve the blind spot of “Delve” creatures. Piling up on extra pieces of removal covering the same threats is not worth the opportunity cost of cutting a good filler combo card from your deck, and is a good way to make yourself end up losing the game with sideboard cards still in hand.

Tasigur, the Golden FangGalvanic BlastGurmag Angler

Again, it’s not about handing a collection of cards for your opponent to shuffle, it’s about presenting a cohesive strategy. Don’t get too much to catch up with the idea of being able to theoretically answer every single type of permanent your opponent can produce. Very frequently I hear players saying that they “need” to add/keep interaction on a specific axis because otherwise, you leave yourself with no way to retroactively get yourself back into the game against certain cards. This is a fear that stems from the willingness to avoid the feeling of helplessness. You have to always keep in mind, though, that in Magic: the Gathering tournaments, match points are awarded for match wins. A match win is a match win, even if you had to dodge your opponent’s perfect draws along the way. A match you lose is worth 0 points, regardless of whether you got steamrolled or you fought until the last turn.

It’s true that your BridgeVine deck cannot really beat a resolved 《Rest in Peace》; it’s also entirely possible your winrate in games where it resolves, but you later deal with it, is abysmal anyways. It’s very likely you are better off not diluting your deck with dead answers, collect your wins in games where you either dodged it or got under it, and ignore your feelings and failings of your human perception in order to yield the best possible winrate you can muster. What it boils down to in the end – frequently, to HEDGE might mean to not take action. Odds are, overboarding cards that look dangerously broad, like 《Engineered Explosives》, 《Collective Brutality》, or 《Surgical Extraction》, might make you look smart 20% of the time, but lower your expected winrate in remaining 80% of the cases by not otherwise being a card that’s naturally more synergistic in your deck.

Engineered ExplosivesCollective BrutalitySurgical Extraction

Dedicated Hatecards

There also exists another class of cards – dedicated hatecards. For the most part obvious and self-explanatory, but to an extent. You would group cards like 《Stony Silence》, 《Leyline of the Void》, 《Eidolon of Rhetoric》, 《Gaddock Teeg》 there. Powerful effects that are relatively simple in their purpose, but there is a way in which people use those cards sometimes that bugs me. It’s attractive to many players to try to create lockout scenarios, where you allow your (typically) combo opponent to execute main parts of their combo, only trying to attack their finisher.

Stony SilenceLeyline of the VoidEidolon of RhetoricGaddock Teeg

This strategy of “cheesing out” people is one that is somewhat valid in very specific game one scenarios but has close to zero effectiveness post-board. Trying to name Ad Nauseam’s 《Lightning Storm》 with 《Pithing Needle》 or stop KCI’s 《Pyrite Spellbomb》 with 《Leyline of Sanctity》? You end up spending a card, and paying mana for it, while your opponent defeats it’s purpose just by virtue of having a certain card somewhere in their deck.

It is typical to frequently board a bounce or a removal spell in combo decks just in case specifically for that reason – player wanting to deploy the hatepiece needs to draw it and deploy it for it to be effective, while the combo player does not need to actually draw the card before the game effectively ends; combo player ends up paying the opportunity only some percentage of the time, while invalidating the lockout card every single time. In short, when fighting combo decks, attack engines. You’d better have a really good reason to attack win conditions.


When boarding in answers, don’t just shiver in fear or auto-include them; always ask yourself whether you think adding them to your deck is actually going to improve your expected win percentage. Always ask yourself whether cutting something that is just a dumb creature or a synergistic card from your own deck for a hatepiece is actually impeding your opponent’s strategy more than yours.

The answer is not always clear, especially at a first glance, and it will require experience and thought. Never stop asking questions, and have a purpose behind your actions.

I hope I managed to convey my thoughts on those matters clearly enough; as a player who loves Modern, I always find the claims about that format being sideboard lottery to not do it justice. Take care & don’t oversideboard.

Until next time,


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