Best-of-One (BO1) Game Mode Guide: Prepare for Day 1 of The Arena Open Tournament!

This guide is a collection of resources that analyse how best to build best-of-one decks, or convert best-of-three decks for best-of-one play, by highlighting key differences between the two modes, the important factors to keep in mind, and some strategies for exploiting those to your advantage. The Arena Open Tournament at the end of this month fast approaches; we’re hoping you’ll be able to make great use this resource to make informed deckbuilding choices for Day 1 (which is best-of-one) alongside our selection of Best-of-one Standard Decks from Pros, Streamers, and Mythic Players. May luck be on your side, but let it be far from the only thing you rely on!

Opening Hand Algorithm

The article above, by my fellow MTG Arena Zone staff member Red5ive, explains how the Arena best-of-one algorithm works, what hand smoothing is, and what this method of pseudo-randomisation changes from the pure randomisation of shuffling/drawing.

Deckbuilding Changes

The article above explains that Hand Smoothing allows you to build decks with generally fewer lands, since you’re more likely to have the first few in your opener. Red5ive highlights some land counts to play to best abuse this phenomenon, and goes over what works best for various deck types. It’s worth noting that this article was made Pre-Companions; these are a pretty strong reason to have a higher land count anyway, especially for the more expensive ones such as Yorion.

Because, as we’re about to delve into, Aggro is better in best-of-one, every deck needs a good core plan for it, whether that’s to win aggro mirrors or to survive long enough to take over the late game. This often takes shape in playing fewer late game haymakers, but if a large proportion of the field does that then Control starts to look much more enticing…

Advantage: Aggro

Aggressive strategies are naturally advantaged in best-of-one for a few reasons:

  1. Many of the cards which hose aggressive strategies are pretty bad against other decks so they come out of the Sideboard.
  2. A strong proactive gameplan makes best use of the lower land count.
  3. Aggro is at its best against any unknown opponent as it does the same consistent thing each time, no matter what you’re up against, and all of your cards work towards the common plan.

Meanwhile, other decks are an amalgam of cards that don’t always operate cohesively together/properly counter what your opponent is doing if you draw the wrong half and such. Aggro doesn’t need to bog itself down with slow greedy cards which midrangey decks absolutely need to win slower matchups, for example.

Companion Tells

Best-of-one is a format designed around limited information, but not no information; being smart with your mulligans is one of the best advantages you can present. For most decks in this Standard environment, you want to mull aggressively, because it’s so easy to recoup card advantage from cards like Narset or Yorion, or just because they can function fine on 6 and many decks are still happy on 5 (even Jeskai Lukka, a Control deck, can recoup most of that card disadvantage on 5 quickly); you want to be fairly aggressive with your mulligans. During the mulligan stage, your opponent gives you a lot of information in their Companion choice, and even if they don’t have one:

  • If they have Lurrus or Obosh, you know they’re likely to be aggressive and it’s imperative to throw away slow hands/those without good anti-aggro tools. As a Control deck, you desperately want removal spells since Flourishing Fox or Valiant Rescuer from Lurrus Cycling can absolutely slaughter you; answering t1 Fox on the draw isn’t easy since it dodges Shock effects.
  • If you’re up against Yorion, that generally means Yorion Lukka or Bant Yorion; if you’re an aggressive deck, you’ll want to pressure them so you don’t want to keep a slow draw. If you’re a Control deck, you’ll want value/tools like Teferi, Narset, Elspeth Conquers Death, Mystical Dispute etc, but probably won’t want creature removal spells all that much.
  • If they have Keruga, that almost always means Keruga Fires; there are some Flash decks that play Keruga but they’re pretty off-meta right now, so I wouldn’t really factor them in. Assuming Keruga Fires, as a Control deck, you’re looking for your Enchantment removal and countermagic. As an Aggro deck, you want a fast curve that ideally doesn’t get absolutely destroyed by Deafening Clarion; they’re likely to have more copies of that card in best-of-one.
  • If they have Kaheera, assume it’s Gruul Fires or a similar midrange beatdown deck. Against those, as a Control deck, you generally want sweepers and removal, alongside ideally just one value spell so you don’t run out of gas. As an Aggro deck, you want removal and cards that let you keep up with their threats, such as Anax and Heraldic Banner in Obosh – a horde of 1 drops won’t do much if you don’t have anything else, when they’re likely to be outsizing you. A few removal spells will get the job done, but you also need to have pressure alongside them. Remember that small removal isn’t great in numbers here; a Kaheera deck probably won’t have any targets other than Kaheera that die to Shock (even something like Paradise Druid only semi-counts), so you only really want one Shock effect.
  • Against Umori, assume it’s Winota or a Mutate deck; you want the same answers for each since they’re just another midrange beatdown deck. See the Kaheera Fires paragraph, but you probably want small removal more since it’s good against Winota.
  • Against Gyruda, prepare for ramp – go as fast as you can and don’t expect to be disrupted too much as an aggro deck. Countermagic is something you want as a Control deck, especially Mystical Dispute, but just aim to have important cards for your deck like Fires of Invention alongside early plays/ways to disrupt them. If your hand has too much removal, consider shipping it.
  • If they have no Companion, it’s likely to be Wilderness Reclamation or a Flash deck, but it could also be Gruul Aggro, a different aggro deck, or an off-meta deck. It’s pretty hard to play around precisely what it could be; you’re mostly going to just look for solid hands here that have a good mix of lands and early plays. Keep in mind what your deck is bad against – if it’s really good against Wilderness Reclamation/Flash and bad against aggro, it makes sense to prepare more for Gruul/other weird aggro decks. It’s best-of-one so aggro decks are going to be more common anyway. You do have a good idea of what decks it’s not (any of the others on this list), which can be nice for narrowing down bad matchups.

Sideboarding for Success

Your sideboard can be a powerful resource that most decks don’t tap into in Best-of-One; the cards which “wish” from your Sideboard (tutor up cards from it) are stronger in that game mode since they have a lot more space to work with in that they don’t have to share with regular sideboard cards, so they have 14-15 slots entirely dedicated to them (depending on whether you have a Companion). Even decks which don’t play one of these cards should have a sideboard, for reasons I explain in the article.

Other Related Resources

Our best-of-one Tier List provides a run-down of which decks we feel are at the top of the food chain right now, and what the best choices are when stacked against each other. The Tier List is updated weekly alongside my Metagame Breakdown, which provides an overview of each deck (it’s intended more for best-of-three but there’s a lot of useful general information there, and you should be able to find whatever deck you’re looking for if you go through the past weeks, which each week links to).

As you’ll need to switch between best-of-one and best-of-three between the days of the Arena Tournament, we recommend having a strong knowledge of both! See my article above, which provides detailed explanations on the key differences between each. That being said, there are parts of it which focus on making the best choice between them, which aren’t ideally suited to this Tournament – you must play best-of-one for the first day and then best-of-three for the second; there is no choice here so those parts won’t be at their most useful to you other than for general information purposes right now.

Wrapping Up

Thanks for reading! Check out or follow me on Twitter/Reddit for regular updates.

Look out for my weekly Mythic Decks of the Week + Commentary, to be released in the next couple of days! Here’s last week’s.

Engage with/show your appreciation for our ever-growing MTG Arena Zone community in the following ways:

  • Discuss our content and ask questions in our Discord server.
  • Follow our Twitter for the latest decks and guides.
  • Subscribe to our Premium membership, where you can browse ad free!

Enjoy our content? Wish to support our work? Join our Premium community, get access to exclusive content, remove all advertisements, and more!

  • No ads: Browse the entire website ad-free, both display and video.
  • Exclusive Content: Instant access to all exclusive articles only for Premium members, at your fingertips.
  • Support: All your contributions get directly reinvested into the website to increase your viewing experience!
  • Discord: Join our Discord server, claim your Premium role and gain access to exclusive channels where you can learn in real time!
  • Special offerFor a limited time, use coupon code L95WR9JOWV to get 50% off the Annual plan!
MTG Arena Zone Premium

Drifter is a draft and strategy specialist, with hundreds of articles under his belt! Of special mention are his Limited Reviews and draft coaching service.

Articles: 502

Leave a Reply