Mickelson's short game exposed at Firestone after time off

Phil Mickelson of the U.S. watches his tee shot on the third hole during the third round of the WCG Bridgestone Invitational golf tournament in Akron, Ohio August 8, 2009.

AKRON, Ohio (Reuters) - World number two Phil Mickelson bemoaned his short game after carding a three-over-par 73 to finish well down the leaderboard at the WGC-Bridgestone Invitational on Sunday.

Back in action after a six-week break while helping his wife and mother undergo breast cancer treatment, the American left-hander showed his competitive rust on the way to a seven-over total of 287.

"I'm encouraged that I was able to get out and play and the biggest thing for me this week was identifying where I was weak," Mickelson told reporters after tying for 58th in the 79-strong field.

"I actually expected to play a lot better than I did. I was playing well heading into the week.

"But it became pretty obvious that when I get on green speeds like this and when I get in rough just a little bit thicker, my short game wasn't where it needs to be."

Mickelson, who had not competed on the circuit since tying for second at the U.S. Open in June, made a solid start at Firestone with scores of 70 and 69 but struggled over the weekend.

After returning a 75 in rain-softened conditions for the third round, he piled up two double-bogeys, three birdies and two bogeys on Sunday to slide down the leaderboard.

"I didn't score well but I didn't play as poorly as the score reflected," three-times major winner Mickelson said after hitting only three of 14 fairways in the final round.

"I thought my short game was not as sharp as it needed to be on greens that got firm, on rough that was a little bit higher than I had been practicing on.

"So I'm going to spend extra time on that getting my chipping down, my putting touch down in preparation for Hazeltine."

The final major of the year, the PGA Championship, starts at Hazeltine National in Chaska, Minnesota on Thursday.

(Editing by Nick Mulvenney)