NEW YORK — Andy Murray rode a roller coaster on Kings Island during the recent Cincinnati tournament, an apt metaphor for the way his comeback from hip surgery has been progressing.

“The last few days, I practiced for a couple of hours each day with some of the players,” Murray said Friday at media day for the upcoming US Open, which starts Monday. “It’s been good. It’s been difficult. It’s just been quite — my tennis has been a bit of stop-starty.”

Murray underwent hip surgery in early January and returned to the tour in June. His ranking is down to No. 378 (he’s entered in the US Open with a protected ranking), and he’s played just seven matches this year (winning four), each small success followed almost immediately by a frustrating failure.

Murray’s most successful outing was at the end of July, in the Washington, D.C., tournament, where he battled through three successive, grueling three-set matches, breaking down in tears at 3 a.m. at the conclusion of the last of those. But he issued a walkover to his next opponent as a precaution against overworking his repaired hip.

In his next start, barely two weeks ago in Cincinnati, Murray lost to No. 16 seed Lucas Pouille.

“All injuries are completely different,” Murray said. “Some are more serious than others. Someone is out for a few weeks with a muscle injury, it’s very different to somebody recovering from a surgery on certain parts of the body. It’s notoriously more difficult.”

Murray has a winnable first-round match Monday with Australian James Duckworth, but he could meet No. 3 seed Juan Martin del Potro in the third round.

The way Murray has been struggling, losing to a high seed in the third round couldn’t be considered a disappointing result. He’s hoping that having the usual day off between matches will mitigate for the demands of the best-of-five set format.

“My body feels better than it did a few weeks ago,” Murray said.

The 31-year-old two-time Wimbledon champion and former world No. 1 spent the past week in Philadelphia, mixing “light” practice with gym work.

“I do feel that once my body is right again — which takes time when you haven’t played many matches in a year — I’m sure that my level will be OK to get me competing at the top of the game again,” Murray said.