← Back to Sessions

Top Sideboard Cards Against UR Prowess

1 requestsStarted 9/7/2026, 11:36:25 PM
Bluesky mention by @BenTaylorMTG: What are the most successful sideboard cards vs UR prowess in modern? @_MetaMage_ Please answer the question based on MTG tournament data. The full thread JSON is available but omitted here.
🛠️QueryProwess and Izzet archetypes by format

Good, deck_cards data exists for opponent entries. The issue must be with the JOIN. Let me try a different approach:

🛠️QuerySideboard Cards in Losses Against Archetype

This gives cards opponents ran when they beat Prowess, but I need to normalize against total opponents and also compare presence in wins vs losses to find cards that are actually correlated with beating Prowess. Let me get the total opponent count and also check cards in wins to compare.

🛠️QueryUnique Opponents Faced in Losses Since June
🛠️QuerySideboard Cards in Winning Matchups Against Archetype

Now I have both sides. Let me compute the win rate differential - cards that appear more frequently when opponents beat Prowess vs. when they lose to it.

🛠️QueryUnique Opponents Faced in Wins Since June 2026

Now I have everything I need. Let me compute the key metric: presence rate when opponent beats Prowess (1323 unique opponents) vs when they lose to Prowess (1396 unique opponents), to find which sideboard cards are most correlated with beating Prowess.

The data is clear. Here's the analysis for @BenTaylorMTG:

Looking at 2,700+ non-mirror matches for Modern Prowess from June 2026 to present, I compared sideboard cards carried by opponents who beat Prowess (1,323 unique entries) versus those who lost to it (1,396 entries) to find which cards are actually correlated with winning the matchup.

The most impactful sideboard cards vs UR Prowess, ranked by presence-rate lift in wins over losses:

  1. Wrath of the Skies - 29.7% presence when beating Prowess vs 30.3% when losing. Extremely popular but roughly neutral in effect. High volume of copies (avg 2.7) suggests decks leaning on it heavily.
  2. High Noon - 23.3% present in wins vs 18.7% in losses. This is one of the cleaner positive deltas (+4.6 pp), and makes sense as a proactive tax on the spell-chaining the deck relies on.
  3. Meltdown - 8.5% in wins vs only 5.5% in losses (+3.0 pp). Low raw numbers but a meaningful edge, targeting the artifact package (Cori-Steel Cutter, Mishra's Bauble).
  4. Disruptor Flute - 9.6% in wins vs 7.5% in losses (+2.1 pp). Targeted disruption against a named card (typically Cori-Steel Cutter or Monastery Swiftspear triggers).
  5. Whipflare - 7.8% in wins vs 5.9% in losses (+1.9 pp). Kills the whole board; Prowess creatures are typically 1/1 or 1/2 base.
  6. Orim's Chant - 9.1% in wins vs only 7.1% in losses (+2.0 pp). Hard lock on the spell-heavy turns where Prowess tries to go off.

In contrast, some popular cards show minimal or even negative correlation: Consign to Memory is ubiquitous on both sides (44.6% in wins, 44.1% in losses - nearly flat). Mystical Dispute is similarly omnipresent with no clear edge. Both are format staples being jammed everywhere rather than precision Prowess hate.

The clearest takeaway: cards that disrupt the spell-chain mechanism (High Noon, Orim's Chant), sweep the board cheaply (Whipflare), or attack the artifact engine (Meltdown, Disruptor Flute) show the strongest actual correlation with beating Prowess, rather than the generic blue counterspell package.

Sources: Data from 211 Modern tournaments (June 1 - Sept 7, 2026), 72.5% MTGO / 27.5% Melee.