Babblelot - that's definitely something that has held Isner back, you're absolutely right. Do you think he'll be able to improve further though, as he's shown a propensity to improve over the years. His latest win over Tsonga in DC with a 3-6 6-7(4) 7-5 3-6 scoreline is I think fairly impressive. On clay, against a solid top 10 player, he won every set with a break, and two sets at 6-3.
He's also been going for a lot more on service returns which I think could pay-off. He's a big guy so additional time on court will hurt him big time but keep in mind his service games are easily at least twice as fast if not faster than most other guys' service games on tour. I'd be interested in seeing his court-time in Indian Wells.
Isner's win over Djokovic at Indian Wells was 166 minutes for a total of 28 games. Roger's win over Nadal was 92 minutes for 19 games. That comes out to nearly 6 minutes per game for Isner and under 5 minutes per game for Roger. Hmm - I expected Isner's per-game statistic to be shorter, that's interesting. I wonder if that's the norm or an exception, Djokovic is afterall not a "typical" opponent for Isner in the first few rounds of big tournaments. It is troubling indeed if he's spending more time per game than other people consistently, given his size and what he should be able to do with a game like his.
Bigger returns might be the key for him. He's now beaten, in Davis cup in recent history, the likes of Federer, Simon and Tsonga in convincing fashion, without going 5 sets vs. anyone, on clay, and winning sets by breaking his opponents. I would say he's on the right path as long as his service games stay quick with at least 2 service winners/aces in each game.