Two-time U.S. Open champion Brooks Koepka announced on Instagram he was withdrawing from this year's tournament at Winged Foot due to a purported injury.

Koepka—who won back-to-back U.S. Open titles in 2017 and 2018—hinted he is dealing with an injury, saying “I'm looking forward to getting healthy and competing at 100% again very soon.”

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Koepka's decision robs the 2020 U.S. Open of one of its biggest stars and a likely contender.

However, it is not a surprise to see the four-time major champion sit out, despite all the success he has had in major championships.

Koepka has dealt with a myriad of injuries over the course of the last two year. He underwent a stem cell procedure on his left knee after playing through a partially-torn patella tendon for much of the season.

This season has mostly been a struggle for Koepka, with injuries again seemingly playing a role. He was treated numerous times throughout the course of the PGA Championship at TPC Harding Park, though he claimed the discomfort stemmed from a hip ailment (via Kyle Boone of CBS Sports):

“It was my hip. Nothing to do with my knee,” he explained of the trainer working kinks out of him on the course. “It's fine. I woke up this morning, it was tight, and worked out and it got even tighter and then we loosened it up. It was a little tight when I was hitting balls on the range but it's nothing to be worried about.”

Brooks Koepka then proceeded to withdraw from the Northern Trust in Boston, and subsequently missed the cut at the Wyndham Championship last month. As a result, he failed to qualify for the FedEx Cup Playoffs.

It remains to be seen just what kind of physical ailment is giving Koepka trouble, but he will not be on hand at Winged Foot next week.