Kevin Kisner surges clear as McIlroy struggles at Quail Hollow

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Kevin Kisner surged clear in the US PGA Championship with a stunning second-round showing on Friday, but Rory McIlroy had to scramble late on in a bid to avoid an early exit.

American hopeful Kisner was tied for the lead after the first round, and a second consecutive four-under-par 67 saw him move four shots clear of Gary Woodland, who had completed two holes, and Thorbjorn Olesen, who had not yet begun his second round.

While the majority of the morning starters struggled with Quail Hollow's thick Bermuda rough, Kisner had no such trouble and was hot with the putter.

Kisner even entertained the fans with a chip-in eagle on the par-five seventh hole - his 16th after starting on the back nine - and he proved low scores are achievable on the course.

Rickie Fowler shot a steady one-under 70 and was three under for the tournament. 

The popular American had two birdies and just one bogey on his scorecard and he remained in contention for a maiden major despite failing to birdie any of the par fives in round two.

Brooks Koepka was also on three under having just started his round, while Chris Stroud is on the same score and yet to tee off.

Unlike Fowler, South Korea's An Byeong-hun finished a roller-coaster round at two under after shooting a 69, which included four birdies, an eagle and four bogeys. 

McIlroy was plagued by a mid-round meltdown that has become a little too familiar at majors.

The Northern Irishman was one under for his round and level par overall through his first 10 holes on Friday, but a run of four bogeys in five holes threatened to derail his tournament.

McIlroy managed to muster back-to-back birdies at the seventh and eighth (his 16th and 17th) to get back to two over and alleviate the threat of missing the cut, but he has plenty of work to do.

The grouping of Phil Mickelson, Jason Dufner and Jimmy Walker combined to shoot 23 over par during the first two rounds. Walker bounced back from an 81 in round one with a two-under 69, but will likely still miss the cut.

Dufner shot four under on his opening nine Friday, but he gave them all back with a five-over 40 on his inward nine. His four-over total through the first two days should be enough to stick around for the weekend.

Mickelson, playing his landmark 100th major, will not be back, though, after shooting a three-over 74 in round two to finish at 11 over.