When I saw the draw I was worried and when Isner lost i was REALLY worried - the more the draw opens up and gives Richard a chance, the worse Richard usually plays.
My thoughts exactly. I think it is a combination of being under pressure and hoping for the opponent to make errors when he plays a lower ranked guy.
One could see that he was tight from the start ( "A must win match"), he rarely discusses with umpires, today he did, more than once. He started passively, the first set was an outright disappointment. When he had understood that he would not get away with it, his level was better, but Istomin served well up to 5-4 in the 2nd set, on 2 or 3 of Richard's bps he came up with aces. The 12th game tells everything, two right out return winners to reach the breaker, in which he did 3 direct BH errors. Positive point: Overall he served well, but not on the breaker.
Istomin was too good, to beat him with an average performance. But still I feel he was beaten by his own attitude, too passive at the start and too much agitation throughout.