When should you side lands in and out?

Question

Some Magic writers advise players to side out a land when on the draw in Limited, in order to improve the probability of drawing a strong starting hand.

• Is it reasonable to do the same (side out a land on the draw) in Constructed? And, if so, why isn't it commonly done?

• Assuming you have a good reason to have land in your Constructed sideboard in the first place (usually cards like Wasteland), when is it strategically beneficial to bring in extra lands instead of only making spell-for-spell substitutions?

Answer 1

A recent case of this was in pre-Avacyn Restored Standard. There were some versions of UB Control that had 3 Nephalia Drownyards main-deck and another one in the sideboard.

In a control mirror with both decks full of reactive cards, the player who has mana advantage usually wins the game, because he or she can play many spells in one turn (e.g. play a threat, counter a removal spell against it, then counter the opponent's counter).

With lands in the sideboard, this deck could side in an extra land, taking out a removal spell. This way they would hit their land drops more easily and have another win condition in the deck, since milling was the best win condition in UB mirrors.

For reference, the 2nd place finisher of GP Baltimore 2012, as Hackworth pointed in the comments, used 2 lands in his sideboard. Its player goes so far as to say that Nephalia Drownyard is "the only card that matters in the mirror."

Answer 2

For the first question, I would say that while the same mathematics work for constructed as well, sideboarding lands just for mana balance reasons in constructed does not seem reasonable.

Firstly, in constructed the impact of a single land on the mana balance of your deck is smaller than in limited due to larger decksize (and the effect is quite small to begin with).

Secondly, in limited you have infinite lands in your sideboard, while in constructed you would have to remove a real card from the sideboard to fit in a land. Since the sideboard cards in constructed typically are very high impact cards in the right situation, this cost is quite significant, and likely higher than any benefit from potentially better mana balance.

Answer 3

Tengfred has already made what I think is the crucial point here: your constructed sideboard allotment is a parsimonious 15 cards. If you're spending slots on the ability to subtly rejig your mana balance between games on the play and on the draw, you're probably doing it wrong.

Having said that, if you can genuinely only find 14 nonland cards that would improve your deck in any imaginable scenario, then I can imagine worse things than a land in the 15th slot. An extra land is almost always going to be a better draw against a creatureless deck than a removal spell, for instance!