1. Stephen Curry. It's the easiest and most obvious answer but quite honestly, the best one. The Cleveland Cavaliers have no one to throw on him in PNR switch or isolation situations. Unless Matthew Delledova runs into his ankles or Iman Shumpert gets even lengthier, I don't see how the Cavs can keep up with Curry enough during his handle like a Mike Conley Jr. LeBron James will certainly have his time on him and that might be the difference in crunchtime, and the series.
2. When LeBron James becomes Peak LeBron James. There isn't necessarily a strategic move I see David Blatt making that punishes the Warriors in any manner. The Warriors can play big against their guy and go small against a James-at-power forward lineup. But if James gets Draymond Green in foul trouble, rains 3s regressing from a 15 percent rate in the postseason, the Warriors will have huge issues.
3. Klay Thompson has been shooting well from 3 but has looked lost in his shot selection and even in off-ball defense. He was locked up by Tony Allen then fell victim to Trevor Ariza. The Warriors haven't needed him much on that end yet but if J.R. Smith is going off, the Dubs will need their own version of that to resurface now.
4. Warriors in 5. Whatever the Cavaliers can do, the Warriors can do better. The Warriors can adjust to any style and even force the Cavs to play in ways that they haven't the entire season. The offense the Cavs run is so 1990s that unless James plays like Michael Jordan, James, and Magic Johnson combined, there's little chance they can force the Warriors away from their comfort zone 4 times out of 7.