Dimir Control's threats — Faerie Seer, Augur of Bolas, Spellstutter Sprite, Ninja of the Deep Hours — are all cheap creatures with total power plus toughness of 5 or less, making Cut Down an efficient, mana-light answer. Hydroblast and Blue Elemental Blast in our sideboard don't have legal red targets here, so they stay out. We trim slower cards like Reckoner's Bargain and one Baleful Strix since this matchup rewards proactive pressure over grindy value against a deck full of Counterspell and removal like Snuff Out.