SCOTTSDALE, Ariz. (AP) -- Phil Mickelson worked a lot harder on his ailing back than his game in the last week. It showed in the first round of the Phoenix Open.
''I did what I needed to do last week and gave it a few days to rest up and get fixed,'' Mickelson said Thursday after opening his defense with an even-par 71.
From the moment he set foot at TPC Scottsdale before dawn, it was clear that the back pain was gone. It also was evident early that his game was a little off.
After effortlessly hitting his opening drive 300 yards down the middle on the par-4 10th, Mickelson dumped a 90-yard wedge shot into the left greenside bunker. He blasted 10 feet past the hole and sighed in relief when his par putt slid in.
On the par-3 12th, Mickelson found the water hazard along the right side. His chip from the fringe stopped about 15 feet short and he two-putted for a double bogey. He three-putted twice, once for par and another for bogey.
''My back is fine. My game was a little rusty,'' Mickelson said. ''I threw away a lot of shots. I made some careless swings. Hitting it in the water on 12 was just pathetic.''
He was seven strokes behind leaders Bubba Watson and Y.E. Yang.
''I got off to a poor start, played a couple over, and finished poorly,'' Mickelson said. ''In the middle of the round, though, I hit a lot of good shots and had a good little run, but it just wasn't quite sharp. I wasn't quite focused on every shot the way I need to be and let way too many shots slide.''
Mickelson first felt soreness in his back two weeks ago in Abu Dhabi, and pulled out of his hometown event last Friday night at Torrey Pines after making the 36-hole cut. He flew to Georgia to see back specialist Tom Boers and was told his facet joints locked up.
''It's fine. Honestly, it's no big deal,'' Mickelson said. ''It was a five-minute fix. I just have to be careful for a week or two as it heals up. It's fine. Mobility is back. It's just not a big deal. ... It happens every now and then.''
After the double bogey on 12, he rebounded with 20-foot birdie putts on the next two holes, but three-putted for par on the par-5 15th after hitting a hybrid pin-high from 245 yards.
''Fifteen really stung,'' Mickelson said. ''It was only a 12- or 15-footer, and I am thinking eagle. I roll it 6 feet by and I miss it coming back. That was costly.''
Mickelson got to 3 under with birdies on Nos. 17, 1 and 4, then bogeyed three of his last five holes. He three-putted the par-4 fifth and failed to get-up-down for par after finding greenside bunkers on Nos. 7 and 9.
''Playing the last five holes at 3 over ... that was really bad,'' Mickelson said.
He hit five of 14 fairways, 11 greens in regulation and had 30 putts.
''I wasn't as sharp as I need to be, for sure,'' Mickelson said.
In his victory last year, he opened with a 60 - lipping out a birdie putt on the final hole - and matched the tournament record at 28-under 256. The 43-year-old former Arizona State star is making his 25th appearance in the event that he also won in 1996 and 2005.
''It's fun to be back here,'' Mickelson said. ''I love playing here.''
Watson and Yang shot 64.
Watson birdied four of the final six holes. The 2012 Masters champion had eight birdies and a bogey.
''If your ball-striking is good, you can shoot some good numbers here,'' Watson said. ''Hit a lot of greens, didn't make too many mistakes, didn't miss too many fairways. Just played solid.''
Yang birdied the final two holes. The 2009 PGA winner also had eight birdies and a bogey, playing the back nine in 6-under 30.
''I think you have to be aggressive,'' the South Korean said through a translator. ''At the same time, you can't be too aggressive. ... You have to really balance it out, but you still have to be a little bit more aggressive than other tournaments.''
Scottsdale residents Pat Perez, Kevin Stadler and Matt Jones were a stroke back at 65 along with Harris English, William McGirt, Greg Chalmers and Chris Kirk.
The crowd was estimated at 88,113, a record for the first round.