One topic I've yet to discuss in detail is the process of building and tuning an effective sideboard, and then using it practically. When examining top 8 decklists, maindeck configurations of the top decks often stay the same week to week, while the sideboards are in a constant state of flux, sometimes radically different between different players. As a metagame develops, so too does its sideboards.

I am preparing for the SCG Invitational this weekend, so this topic is fresh in my mind; it's a process I am actively engaged in. There is a thought process that winning players go through when approaching sideboarding, and today I'll share what is going through their head, including general theory and practical tips for constructing and tuning an effective tournament sideboard, and using this sideboard effectively.

Rules of the Effective Sideboard

A sideboard deck is used between games of a best-of-three or best-of-five match, where any number of those cards can be substituted for cards from the maindeck. Alternatively, a recent rule change allows sideboard cards to be added to the maindeck without substitution, but, from a practical competitive standpoint, this is a poor idea in all but the most extreme cases because it dilutes the quality of the deck, making said sideboard cards less likely to appear.

A 15 card sideboard constitutes 20% of the total 75 card pool in a deck, and can be used to change up to 25% of the 60 maindeck cards. Sideboards are used for the majority of games in an average match, so they exert considerable influence.

Theory of the Effective Sideboard

The role of a sideboard in tournament Magic is to better adapt the deck to compete against other decks in the metagame. An effective sideboard cannot be built without strong knowledge of an archetype and its niche within the broader metagame. This brings up the matter of determining the metagame for a specific tournament. Assuming perfect knowledge of a metagame, a perfect sideboard could be built for attacking it.

It's a common fallacy for players to fill sideboard cards with cards to combat every deck in the metagame. While this strategy may seem sound, it's often the case that a weak matchup is such a small portion of the metagame that it's wiser to simply ignore it, saving valuable space for more common enemies.

It's also very much possible to "win-more" by bringing in too many cards against an already favorable matchup. It's much more practical to identify a deck's most common, weakest matchups in the metagame and build a sideboard to combat those decks. By attacking the decks that pose the biggest problem, the sideboard can shore up weaknesses in an archetype and give it a strong ground for fighting against the field.

Designing a Sideboard

There are various ways to select sideboard cards. An important trade-off to consider is power versus scope. Often the most powerful sideboard cards will only be effective in one matchup. If the matchup is weak and common enough, then perhaps this sort of card is ideal. Other sideboard cards may be broadly applicable, but not necessarily high-impact. The best sideboard cards will be high in impact and broad in scope, and it's the truly rare sideboard card that scores high in both categories.

For example, I play Duress in my Standard Monoblack Devotion sideboard to combat UWx Control decks.

It removes nearly anything in their hand from turn one to turn twenty, making it quite powerful. And, at one mana, it's quite efficient.

It turns out that Duress is also incredibly effective against Boros Burn, because it gives the black deck a way to interact with the cards in the Burn deck, something it normally has trouble doing.Duress has also proven to be effective at combatting Jund Monsters, because they may play more noncreature spells than creatures post-sideboard , including highly-potent planeswalkers that give Monoblack Devotion fits. For these reasons and more, Duress is very powerful and broad in scope, making it an ideal sideboard card that typically takes up four slots.

Another, more extreme method of sideboarding is to completely change the gameplan of the maindeck. This is a topic I covered over the last two weeks, so check out that series for more information on what's known as the "transformational sideboard", part one, and part two.

One of the most important aspects of sideboarding is not what to bring in, but what to take out.

There are cases where maindeck cards in a matchup are quite weak, such as creature removal against a control deck. In these instances, it's important that the sideboard contains enough effective cards to replace all of the potentially weak maindeck cards.

In a wide open metagame, or in a deck that often has ineffectual maindeck cards to side out, it will be a good idea to fill a sideboard with cards broad in scope.

The Process

When it comes to figuring out what comes in and what goes out, top players already have a plan.

Well before a tournament, players will have already laid their deck out on the table and determined their plan for specific matchups. The sideboard is designed with this in mind and will interface flawlessly with the maindeck, where strong sideboard cards replace the weakest cards in the maindeck depending on the matchup, leaving no useful sideboard card behind and no weak maindeck card remaining.

It's a common flaw for players to fill their sideboards with theoretically strong sideboard cards, only providing marginal value, so it's very important they have a high-enough impact to warrant inclusion. There was a period of time when Monoblack Devotion would play a high number of Dark Betrayal in the sideboard. It was great for combating the mirror match, but players would usually cut Hero's Downfall in order to find room.

Sure, the sideboard card was a bit more efficient, but cutting creature removal for creature removal is not necessarily a sound sideboard strategy. When Pack Rat defined the mirror, Dark Betrayal could be considered a dedicated answer to that card, but the advent of Bile Blight changed the matchup and made the hate unnecessary. Thus, Dark Betrayal has been seen less and less as time has gone on.

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In a world where maindecks are pined over, shared, tuned, refined, the process iterated constantly, the sideboard is often overlooked, considered a last-minute thing to worry about, even looked at by some as an inconvenience. Remember that the sideboard is an extremely powerful tool, and honing sideboard skills and spending the time practicing and thinking about your matchups will yield dividends to the tournament player.

When it comes to sideboarding, what aspects do you find to be the most troublesome and confusing? Anything you'd like to see me cover? Post in the comments!