Arnold Palmer Invitational presented by MasterCard: Carded a final-round, 2-under 70 on a Monday finish to defeat Justin Rose by two strokes at the Arnold Palmer Invitational, winning the event for a PGA TOUR record-tying eighth time (Sam Snead at the Greater Greensboro Open). His 77th career PGA TOUR win moved him within five wins of all-time leader Snead's 82 victories. With wins at the Cadillac Championship and Arnold Palmer Invitational, he won in back-to-back starts for the first time since the 2009 Buick Open and World Golf Championships-Bridgestone Invitational. Supplanted Rory McIlroy for the No. 1 position in the Official World Golf Ranking. The last time he held the top spot was on October 30, 2010. Surpassed Ernie Els for most weeks in the top 10 of the Official World Golf Ranking, at 789. Had a record run of 736 consecutive weeks in the top 10 from April 13, 1997, to May 15, 2011. Returned to the top 10 on March 25, 2012, where he has since remained. Of his eight Arnold Palmer Invitational wins, has entered the final round with at least a share of the 54-hole lead seven times. Made his 17th start at the Arnold Palmer Invitational, with his lone missed cut coming as an amateur in his first start, in 1994. He has played in every event at Bay Hill since, with the exception of 2010.
The Open Championship: Finished T6 at the 147 Open Championship at Carnoustie, his first top-10 in a major since at T6 at the 2013 Open Championship. Week was highlighted by a third-round 66, his lowest round in a major since a 66 in the second round of the 2011 Masters. Was just his second made cut (2018 Masters Tournament/T32) in his last six major starts. Posted rounds of 71-71-66-71, the first time since the 2010 Masters Tournament (T4) he recorded four par-or-better rounds in a major. Paired with eventual-champion Francesco Molinari, entered the final round four shots off the lead. Took the solo-lead at 7-under after nine holes, one ahead of Molinari and Jordan Spieth, but his lead disappeared with a double bogey at No. 11. Bogeyed No. 12 and birdied No. 14 before closing with four pars to finish at 5-under. The finish moved him to No. 50 in the Official World Golf Ranking, returning to the top 50 for the first time since January 2015. The ranking also earned him a spot in the World Golf Championships-Bridgestone Invitational.
Surgery: Pulled out of next two PGA TOUR starts, the Genesis Open and The Honda Classic. Released statement: "My doctors have advised me not to play the next two weeks, to continue my treatment and to let my back calm down. This is not what I was hoping for or expecting. I am extremely disappointed to miss the Genesis Open, a tournament that benefits my foundation, and The Honda Classic, my hometown event. I would like to thank Genesis for their support, and I know we will have an outstanding week." In April, announced on his website he had undergone further back surgery. The operation was performed by Dr. Richard Guyer of the Center for Disc Replacement at the Texas Back Institute.
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