THE WOODLANDS, Texas (AP) — Defending champion and world No. 2 Lilia Vu withdrew from the Chevron Championship on Thursday before the first round because of a back injury.

She issued a statement on Instagram saying she had “severe discomfort” in her back during warmups Thursday to force her withdrawal.

“I have been dealing with a back injury for a while now,” she said in the statement. “Some days are better than others, and today was unfortunately not a good day. During my normal warmup routine, I had severe discomfort in my back and I felt that I could not compete up to my standards and made the decision to withdraw from the tournament ahead of my tee time.”

She added that she was returning home immediately to see her doctors and determine the next steps.

The back issue forced her to withdraw from a previous event this season.

The 26-year-old American was asked about her health leading up to the tournament on Tuesday.