Rory McIlroy's quest for a calendar Grand Slam just hit an unexpected roadblock—and it's all coming down to a blister on his right pinky toe.

The four-time major champion cut his practice round short at Pennsylvania's Aronimink Golf Club on Tuesday, walking off the course after just three holes. According to reporters on site, McIlroy was visibly uncomfortable throughout the abbreviated session, repeatedly removing his right shoe and examining his foot before ultimately heading back to the clubhouse.

ESPN later reported that McIlroy was spotted in the locker room trying on different shoes, searching for a solution to the nagging issue.

The blister first became a problem during last weekend's Truist Championship. McIlroy managed to play through the discomfort but was seen limping during the final round at Quail Hollow, where he finished tied for 19th in his first tournament since winning the Masters. While he downplayed the injury after shooting a final-round 67 on Sunday—refusing to use it as an excuse for his third-round 75—it was clear the issue was on his mind.

Coming into this week's PGA Championship, McIlroy had already scaled back his practice schedule, planning to play just nine holes Tuesday and nine Wednesday to take pressure off the blister. After Tuesday's early exit, it remains to be seen whether he'll be able to get in those nine holes Wednesday before the tournament tees off Thursday.

For a player chasing history with a Grand Slam bid, every detail matters—right down to the shoes on his feet. Golf fans and fashion enthusiasts alike will be watching closely to see how McIlroy manages this unexpected hurdle at Aronimink.