When you flop the absolute nuts on a monotone board, checking back allows your opponent to catch up or bluff into you.
Flop Analysis
Flopping the nut flush is a dream scenario, but checking is a high-frequency play to protect our checking range and trap the BB.
**Ranges:** We hold the As, which is the most important card on this board. By checking, we allow BB to continue with their Kx, 7x, and small spade draws that might fold to a bet, while ensuring our checking range isn't just weak air.
**Board:** Monotone boards are extremely static. Since we have the board locked down with the nuts, there are very few turn cards that can hurt our actual hand strength, making a slowplay very attractive.
**Sizing:** If we do choose to bet, a small sizing (33% pot) is preferred to keep BB's wide range of pairs and weak draws in the pot.
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> **Takeaway:** On monotone boards, checking back the nut flush protects your range and prevents your opponent from playing perfectly against a polarized betting range.
Turn Analysis
The Ace is a great card to start building the pot as it likely hits the BB's range of 'catch-up' hands.
**Ranges:** After checking the flop, our range looks like Kx, Ax, or missed broadways. Betting now targets BB's newly improved Ax, Kx, and any spade draws they decided to lead or check-call with.
**Blockers:** Holding the As is a double-edged sword; we have the nuts, but we block the very card (the nut spade) that BB would use to call down or bluff with. This makes checking again a viable mix to let them bluff the river.
**Plan:** Since we bet small and they folded, we missed out on value, but against a range that completely whiffed this runout, there wasn't much to be gained. On most rivers, we are looking to go for a large value bet if they call here.
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> **Takeaway:** When the board brings an overcard to the flop, it's time to start extracting value from the hands that just improved to second-best.