British Open champion Phil Mickelson believes his best is yet to come despite recording only one top-10 finish this year.

Mickelson won the British Open at the 20th attempt last year at the age of 43, just seven days after picking up his first title on British soil in the Scottish Open.

But since then the 44-year-old, dogged by health issues caused by suffering from psoriatic arthritis, has struggled to recapture his best form.

“Obviously it hasn’t been a good year,” Mickelson admitted on Monday after returning the Claret Jug to R&A officials ahead of his Open defence at Hoylake.

“Normally I would be discouraged or frustrated, but I’m just not. I feel like I’ve had some good breakthroughs in some areas.

“I haven’t had the results, I know I haven’t played well. But the parts feel a lot better than the whole right now.

“I don’t know when it will all click together. I don’t know if it will be this week, in three weeks or a month or what, but it should be soon.”

Mickelson’s victory at Muirfield 12 months ago made him the third consecutive British Open champion over the age of 40, following on from Darren Clarke at Sandwich in 2011 and Ernie Els in 2012.

His main focus is now on winning the US Open, a tournament he has finished runner-up in a record six times, to join Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus and Tiger Woods in claiming all four major titles.

But the world number 13 is quick to deny any suggestion that his motivation to win further titles at the other three majors is on the wane.

“I actually feel better than I have in years and I’ve had to work a little bit harder,” added Mickelson, who withdrew from tournaments in San Diego and Texas earlier this year with back and muscle injuries respectively.

“I believe that the next five years are going to be some of the best in my career.”