ORLANDO, Fla. – As Jordan Spieth was getting off to a scorching start Saturday at Bay Hill, his playing competitor, Justin Rose, still hadn't gotten warmed up.

Rose began the third round at 5 under and just four shots off the lead at the Arnold Palmer Invitational, but he said he woke up Saturday morning with some back issues. As Spieth began his day birdie-ace and then orchestrated an unreal par save at the third hole, Rose was laboring.

The Englishman put three balls in the water at No. 3, made a quintuple-bogey 9 and then chose to withdraw before completing four holes.

"Disappointing to have to WD," Rose said. "It's been an exciting week, playing back in front of fans and, obviously, quite a visible WD playing with Jordan out there. ... Just kind of woke up with a bit in a sort of spasmmed lower back today and tried to kind of get through it. My warm-up was hard work, and I just couldn't stay down in a shot. I missed basically every golf shot left to start the day. Even my little chip into the fourth hole out of the rough from the lefthand side was creating pain.

"And with the eye on next week and what have you, I just felt like it was a prudent call, just to call it at that point. But I felt bad with Jordan having momentum to sort of change, change the vibe of the group."

Spieth will now play the rest of the round as a single.