Jordan Spieth believes he is close to recapturing his best form after finishing tied for third at the US PGA Championship.

The three-time major champion posted his first top-10 finish since last year's Open Championship, ending up six shots behind winner Brooks Koepka.

Spieth has fallen to 30th in the world rankings after a tough run, but feels he is nearing the form that saw him win three majors from 2015 to 2017.

"It says that I have full belief in our team. I have full belief in my process, my mentality, my selfishness and my work ethic," he said.

"I put in more hours over the last five months than I've ever put in my game in a five-month stretch, just trying to get to where I can be out here on a major championship Sunday making par saves, making birdie putts, and contending even without having my best stuff.

"That's like 2015, 2016, 2017, that's how I felt then."

Spieth fired a one-over 71 in the final round at a tough Bethpage Black, where he felt it was always going to be difficult.

The 25-year-old said: "I knew coming into the week that it was unlikely on this golf course that I was going to have a chance to win.

"That's a humbling feeling for me, but I knew that if I played the course the right way, had the right mentality, kept putting the way I've been putting, that I would be in it; that I would be, you know, in and having a chance to make some noise."