John Isner has always played better inside the United States (and Canada) than elsewhere. He just has. He has recognized that fact, although unfortunately he does not seem to have been able to counteract it. 

Of Isner's nine titles (all of them at the 250 level), eight have come on American soil. Of his nine career runners-up, again, eight have come on American soil. He has reached the semifinals of five Masters tournaments with only one of them being outside the Americas (Bercy in 2011). Isner's best result at a Grand Slam is still his US Open quarterfinal showing in 2011, and on the average it's his best Grand Slam.

There have been questions about Isner early in this year. He did not look great in a third-round Australian Open loss to Gilles Muller and played pretty poorly in Memphis a few weeks later. Isner's lack of form really stretches back to last year's US Open, where he also lost in the third round. More recently, Isner has fallen out of the top 20 for the first time in two years, although a win over Nishikori in the Miami quarterfinal would bring him back up.

What has many the most concerned for Isner, though, was his Davis Cup showing a few weeks ago. He played one of the least aggressive matches we have ever seen from him and lost a 15-13 set to (then) world No. 111 James Ward. It was far from Isner's finest, to say the least. Still, he bounced back well at his last tournament in Indian Wells, reaching the round of 16 with a solid win over Kevin Anderson before challenging Novak Djokovic in a tight loss. This week he is showing that playing in the States is what he does best, again, as he just gutted out a three-tiebreak win over Milos Raonic. 

Isner is really at where he has always been in his career. Sticking around the top 20 or so, potentially a threat to make deep runs at big tournaments, but just never quite able to get over that hump.

I won't turn this into another “what Isner can fix” or “what Isner needs to do to win big tournaments” piece. We've seen plenty of those. I will just comment, though, that when Isner is in tough places against top opponents, he becomes very aggressive on his opponents' serves. Against Djokovic in Indian Wells, with Isner down 6*-4 in the tiebreak, he went after a Djokovic serve with a massive forehand and followed up with another massive forehand for a winner. It was a perfect example of the damage Isner can do when he just swings free on an opponent's serve. I just wonder what he can accomplish if he does that more often–maybe, even, when he's not in danger of losing the match.