"Why is that card still in your deck?"

"I can't believe I lost to Unmoored Ego. That card is unplayable"

Oftentimes, as Magic players, our understanding of sideboarding is limited to what we read and what we hear from others. We understand if you're playing an Arclight Phoenix deck against control your Shocks are on the weaker side of the spectrum and are easy enough to board out. In Legacy your Lightning Bolts against Miracles and Grixis can often look like they fall completely flat. For a deck like Grixis Delver it's commonplace knowledge that Daze and Force of Will are the easy board outs in the fair matchups. But more often than not you end up losing to these cards that your opponent was supposed to board out. What's the deal? Is your opponent wrong and lucky? Or is there something more? To tell the truth this can often feel like a very fine line, but in Magic the truth is a lot of the points we gain in matchups are based around concrete game plans rather than sideboard cards. While it's true that your sideboard cards will have an impact on the game, more often than not it is a one hit knockout.

This isn't going to be an article about sideboard guides, just thought processes behind it.

Let's start with an example in Legacy. We can start by viewing the average deck lists for Grixis Delver and Miracles.

Grixis Delver | Legacy | Rudy Briksza

• Creatures (11)
• 2 Gurmag Angler
• 2 Young Pyromancer
• 3 True-Name Nemesis
• 4 Delver of Secrets

• Spells (30)
• 1 Dead // Gone
• 2 Spell Pierce
• 4 Brainstorm
• 4 Daze
• 4 Force of Will
• 4 Lightning Bolt
• 1 Preordain
• 1 Thoughtseize
• 3 Inquisition of Kozilek
• 4 Ponder
• 2 Bitterblossom

• Lands (19)
• 2 Flooded Strand
• 2 Misty Rainforest
• 2 Polluted Delta
• 2 Scalding Tarn
• 3 Volcanic Island
• 4 Underground Sea
• 4 Wasteland

• Sideboard (15)
• 1 Pithing Needle
• 1 Grim Lavamancer
• 2 Abrade
• 2 Diabolic Edict
• 1 Flusterstorm
• 2 Pyroblast
• 1 Red Elemental Blast
• 3 Surgical Extraction
• 1 Liliana, the Last Hope
• 1 Marsh Casualties

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Miracles | Legacy | Rudy Briksza

• Creatures (5)
• 2 Monastery Mentor
• 3 Snapcaster Mage

• Planeswalkers (3)
• 1 Teferi, Hero of Dominaria
• 2 Jace, the Mind Sculptor

• Instants (19)
• 1 Counterspell
• 2 Spell Pierce
• 4 Accumulated Knowledge
• 4 Brainstorm
• 4 Force of Will
• 4 Swords to Plowshares

• Sorceries (9)
• 2 Council's Judgment
• 3 Terminus
• 4 Ponder

• Enchantments (4)
• 2 Back to Basics
• 2 Counterbalance

• Lands (20)
• 1 Mountain
• 2 Plains
• 5 Island
• 1 Arid Mesa
• 1 Volcanic Island
• 2 Tundra
• 4 Flooded Strand
• 4 Scalding Tarn

• Sideboard (15)
• 2 Containment Priest
• 1 Engineered Explosives
• 2 Flusterstorm
• 1 Gideon, Ally of Zendikar
• 1 Hydroblast
• 2 Pyroblast
• 1 Red Elemental Blast
• 1 Rest in Peace
• 2 Surgical Extraction
• 1 Vendilion Clique
• 1 Wear // Tear

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Glancing at the deck lists we can see some problematic cards off the bat for Delver. Cards like Jace, the Mind Sculptor, Back to Basics, Terminus, and Monastery Mentor are going to be some of the more relevant cards we're going to want to answer. So take Lightning Bolt; while normally a dead card, some amount of Lightning Bolt gains value. Your Blasts will be stressed easily given the sheer amount of power cards they could target. Seeing Monastery Mentor it's pretty reasonable to want to include some removal that can take it out on the spot, and sometimes being able to just go upstairs with Bolt can end a game quick. This doesn't change the fact that Lightning Bolt is very weak here. It's not something you want rotting in your hand thanks to minimal targets and its generally an awful top deck when you need board presence. So, if we can reason that Lightning Bolt is usually mediocre but flexible in some spots, then we'd want it post board, even if it isn't in high numbers.

We can apply this same reasoning to other decks as well. For example, let's look at the classic control deck. It has become standard for control decks to build a sideboard filled with creatures. Last Standard season the control decks had a minimum of History of Benalia to take advantage of decks that side out all their removal.

It's important to visualize how you want your main deck to look in each matchup when you're building your sideboard. I've been doing this by starting out with a 75 card main deck and then I decide which 15 cards I don't want based on my concrete game plans against every deck. When you sit down across from an unknown deck, understanding your deck's different configurations can help facilitate easy sideboarding in any given matchup.

I think some players trap themselves with rigid sideboard guides and can miss when to shift gears or ways to counteract opponent's sideboard plans. Your sideboard plans should also consider your opponents' plans as well. Read articles and watch players; have a chat post match with your opponent to gain some insight into their sideboard plans. This is a good way to learn and internalize good sideboarding principles.

Then again, sideboarding isn't always clear cut. Based on our earlier discussion, we can see some cards will be bad in a matchup no matter what, and there are cards that will always be debated. For example, consider Force of Will and Daze in fair matchups. It used to be commonplace to board them all out, but Delver decks have slowed down a ton and there are more bombs you need to answer. Having counterspells makes life better. The other day I tweeted a poll and realized there wasn't a true consensus on how to board in the Standard Golgari mirror.

This poll was extremely close even after a few hundred votes. I think this goes to show how difficult sideboarding can be. To complicate matters further, Reid Duke said in his article to board Wildgrowth Walkers out and gave great reasons to do so, but Caleb Durward compared the card to Tarmogoyf in his call to leave them in. Personally I feel like the matchup centers around Find // Finality and Carnage Tyrant, so having a board presence and extra life to play with means you can't be eked out as easily and Wildgrowth Walker getting massive means it's a must kill target. My reasoning ALSO takes into account how other players are sideboarding. We can see many players lean on extra Tyrants and board out some number of Cast Down. Because of this I feel more comfortable leaning on a cheap creature that grows larger, is harder to remove, and demands an answer in the short term. It helps clear the way for planeswalkers and gives you more time to find the answers you need.

At least, that's how I think about it. I have a game plan set in motion that dictates how I want to play the mirror and how I expect it to play out. Having a better plan has improved my game and I hope it helps improves yours too.

Sideboarding isn't an exact science and it's important to know more than just the cards to board in and out. You have to understand the whys and hows. Knowing your board plans and your opponents' will help gain you ton of percentage points.