You can tell that Ryan Harrison is getting serious about his tennis when you look at his dinner plate. “The nutrition side of things is something I didn’t pay as much attention to in the last few years,” Harrison said. “In the last six months it’s been getting more important.”

The 19-year-old American’s new focus on his diet paid off last week in Indian Wells, where he beat Flavio Cipolla, Viktor Troicki and Guillermo Garcia-Lopez before losing to Gilles Simon in the fourth round. Harrison put his form in California down to broccoli.

“I actually hate broccoli,” he said. “I was sitting there with my coach at dinner the night before I played Cipolla and he started laughing. He said: ‘If you eat that broccoli you’re going to win.’ I was like: ‘You promise?’ He was like: ‘Yeah.’  So I ate it, I played a great match, and so then I ate broccoli again. It looks like I’m going to be eating it for a while until things don’t go well.”

However, Harrison is not following Novak Djokovic’s gluten-free diet. “I’m not as crazy as Novak yet – and that’s a joke, by the way,” Harrison smiled. “He’s obviously doing it for a good reason. He’s made the commitment, and that’s obviously paid off for him, being able to play a high level of tennis for six hours, which is unheard of before. I’m working my way towards that sort of thing, but I still like my good foods. I’ll eat something to treat myself every now and again.”

Harrison equalled his previous best performance at a Masters 1000 event by reaching the last 16 at Indian Wells, which matched his achievement at the tournament last year, when he eventually lost to Roger Federer. This week the world No.73 is playing in Miami, where he faces Italy’s Potito Starace in his opening match. Victory would give him another crack at Federer in the second round.