"I got a little sick yesterday walking up to the 13th green," he said after posting a two-under 214 total with one round left at the Sawgrass TPC.

"I had a really sore throat last night and a lot of energy was drained, so I started taking some antibiotics.

"I'm starting to feel a little bit better today. I didn't really warm up today, and tried to conserve a little energy."

Mickelson refused to concede defeat, not with the three players ahead of him somewhat vulnerable for different reasons.

"Today I could have very easily shot a 67 or 68 but I let it slide to 71," he said. "Tomorrow, I need to shoot something in the mid-to-high 60s to have a chance.

"Hopefully we'll be able to put together the score that I need. I'm playing well enough to shoot that round."

Mickelson admitted it made a difference that a certain player was not ahead of him: "When Tiger (Woods) is playing, you feel like you've got to make birdies to catch him," he said.

The world number two switched putters for the third round, going back to the old mallet.

"I didn't putt the way I wanted yesterday, so I went to the putter I won with last year," he said.

"The short ones weren't as confident (on Friday) and the line on that mallet makes it easier for me to line them up."

From Andrew Both, PA Sport, Sawgrass