TORONTO, Canada (AFP) — Five-time major champion Brooks Koepka withdrew before the final round of the PGA Tour Canadian Open with a hand injury on Sunday, less than a week before he is due to tee off in the US Open.

Koepka, who has returned to the PGA Tour from the breakaway LIV Golf league, won the second of his two US Open titles in 2018 at Shinnecock Hills, where this year's championship starts on Thursday.

A stand-out performance on the greens on Thursday saw Koepka tied for the lead at TPC Toronto Osprey Valley after an opening round 64.

But on Saturday, he carded a two-over par 72 and told reporters after the round he was struggling with a mysterious hand problem.

"Yeah, I don't know what it is," Koepka said.

"I'm struggling to grip the club with my ring finger and pinkie finger, so can't grip it. So the club is kind of just my fingers would come loose; it was kind of numb. I don't know what the deal was, but hopefully we'll figure it out.”

"The whole warm-up, I felt fine, I was absolutely good. Then got to the range and went to grip the club and I just couldn't even grip it. So it lasted — it was all day.”

"Felt better the last few holes.”

"I don't know if that's just the meds kicking in or what it is," he added.

Koepka, who withdrew shortly before he was due to tee off on Sunday, has one top-10 finish in 11 starts this year after making his return to the PGA Tour at Torrey Pines in January.