This week at TPC Sawgrass was supposed to feature all top 50 players in the Official World Golf Ranking, the first event to do so in almost two years. That will no longer be the case.

Paul Casey informed officials on Wednesday (US local time) that he has withdrawn from the 2018 Players Championship. Casey, ranked 12th in the world and 10th in the FedEx Cup, has bowed out due to a back injury. He received treatment on Wednesday morning at the course, but was advised by medical staff to sit the tournament out rather than risk further ailment.

It’s a tough break for the 40-year-old, who’s continued to enjoy a late-career revival in 2018. Casey entered Ponte Vedra Beach with seven top 15s in 11 events this season, including his first win since 2009 at the Valspar Championship. He posted a T-5 at last week’s Wells Fargo Championship, and ranks sixth on tour in strokes gained.

Surprisingly, this is the third time in 11 visits to TPC Sawgrass that Casey’s had a W/D. He suffered a shoulder issue in 2012, and ended his 2015 tournament early following a first-round 79 due to illness. His best finish was a T-10 in 2004.

Taking Casey’s place in the field is Keith Mitchell. The 26-year-old is a recent Tour graduate, and currently 76th in the FedEx Cup standings. His best finish this year is a runner-up at the Corales Puntacana Resort & Club Championship.