TUCSON, Ariz. — Mike Weir went on a back-nine birdie binge to take control of the Cologuard Classic.

Phil Mickelson waded into the mud for the second straight day and will have to dig out of a deep hole if he’s going to make history.

Weir shot a 5-under 67 to build a two-shot lead in the Cologuard Classic on Saturday, leaving Mickelson with a lot of ground to make up to win his third straight PGA Tour Champions start.

“I can’t recall a time where I’ve hit so many shots close to the hole,” Weir said. “I’ve hit really a lot of shots that have been almost tap-in to just outside of tap-in. My wedges have been very good, even mid iron game’s been very good, and I’m driving it good.”

Weir shot 66 in the opening round and had eight birdies in breezy conditions at tricky Tucson National. The Canadian left-hander was at 13 under, with Kevin Sutherland second heading into the final round.

Fellow Canadian Stephen Ames is in a tie for 42nd place at even par.

Tim Petrovic became the second player in PGA Tour Champions history to have a hole-in-one in consecutive rounds with an ace on No. 14. He was 8 under after a 67.

Mickelson is bidding to become the first player to win his first three career starts on a PGA Tour-sanctioned tour. The five-time major champion was nine shots back after a 72 that included a second straight day of hitting out of the mud on No. 15.

Mickelson was the last amateur to win a PGA Tour event as 20-year-old in Tucson 30 years ago, but has burned the edges of holes through two days in his return.

“I really don’t know what to say other than it just was fractionally off the whole time,” he said. “I thought I hit a lot of good shots that just weren’t ending up close and I just wasn’t able to score. I scored terribly today, obviously, and relative to how I play.”

Lefty hit into the large wash dissecting the course for the second straight day, pulling a drive on the par-5 second after doing the same on No. 13 Friday. He had a stretch of three birdies in four holes after the double bogey on No. 2 and another on the par-5 12th when he got up and down from a greenside bunker.

Mickelson hit out of the mud on the par-5 15th in Friday's opening round after a 5-iron rolled farther than he expected and trickled into the pond on the dogleg right. He hit driver in the second round and ended up with the same result when his ball landed on the fairway and caromed hard right.

Mickelson left his shoes on for his mud shot in Friday's round and made a 4-foot birdie putt after slopping it out. He opted to take his shoes off for his second muddy go-round and had another birdie chance despite spraying himself with mud, only to watch the putt slide by the hole.

“I’m doing something wrong, so I've got to fix that,” he said. “I don’t know what to say. I hit two really good shots that have both ended up in the water. I can easily play more left, but then I can’t get there. Then I can’t get that second shot there and I’m trying to make a 4.”

Weir shot 1-under 35 on the front nine before going on a birdie binge. The 2003 Masters champion ran off a string of seven birdies in eight holes to start the back nine, but a pulled approach shot on the par-4 18th led to a bogey.

Petrovic had an ace on No. 16 in the opening round and pulled off rare consecutive-day aces on the 186-yard 14th Saturday. Petrovic raised his hands in the air as the handful of fans cheered, then curled up into a fetal position on the tee box after watching another improbable ace.

The only other PGA Tour Champions player with aces in consecutive rounds was Graham Marsh at the 2004 Senior British Open.

“I heard someone say, “Go in,” and I’m like, `No, it can’t -- there’s no way, I just had one yesterday, and it’s been six years since I had the one before that,'” Petrovic said. “I just flopped on the ground and then I kind of got in the fetal position. That’s all I could do.”

Sutherland had four birdies and eagled the par-5 17th to shoot a bogey-free 67.

Scott Parel was three shots off the lead after a bogey-free 67 that included five birdies.