Collin Morikawa withdrew from the Valero Texas Open on Tuesday due to back spasms, putting his availability for the upcoming Masters in jeopardy.
Frankie Capan III will participate in this week's tournament in San Antonio in place of Morikawa, 29, who hasn't played since withdrawing from The Players Championship on March 12.
A two-time major champion, Morikawa is the world's eighth-ranked golfer.
In five events so far this season, Morikawa has a win at the AT&T Pebble Beach Pro-Am and two top-10 finishes – a tie for seventh at The Genesis Invitational and fifth at the Arnold Palmer Invitational.