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On a day when the course conditions favored experienced players with major championship success, PGA Tour rookie Michael Thompson had to learn on the fly.

The Hooters Tour just didn't prepare him for anything like this.

Facing rough so thick it forced Mike Weir to withdraw with an elbow injury, and the tightest course he's ever seen, Thompson followed up his even-par opening round with a 4-under 66 on Friday to move into a tie with fellow American Chad Campbell after the second round of the Canadian Open.

"I played on the Hooters Tour last year, which there's no rough," Thompson said. "You just take your driver out and kill it."

That hasn't been the recipe for success this week, not with the long grass being compared the U.S. Open, fairways around 27 yards wide, and old growth forest lining every hole on the 7,010-yard Shaughnessy Golf and Country Club.

For Thompson, a 26-year-old from Alabama who was the rookie of the year on the Hooters Tour last year, the only comparison was the 2007 U.S. Amateur, where he made the finals before losing to Colt Knost, who was at even par Friday.

"What I've learned on a golf course like this is you pick your line and you get really focused in on your target," said Thompson, who has now made five straight cuts in his first PGA Tour season, and 10 of 17 overall.

Playing under mostly sunny skies in the afternoon, Thompson followed an early bogey with five birdies, including one on the tough 472-yard, par-4 18th.

"On top of that, just accepting where it goes," he said. "If it goes in the rough, you deal with it. There's no reason to freak out or panic."

It's a lesson many of the leaders this week had already learned.

Campbell, coming off a season-best tie for fifth at the British Open, shot 67 under cloudy skies in the morning. Playing partner Paul Goydos (69), and Lee Janzen (68), a two-time U.S. Open champion, also had shares of the lead before bogeys on their final hole dropped them to 3-under on another tough day.

"The toughness of the course I think is great, especially if you have good experience on it," said Janzen, whose last win was the 1998 U.S. Open. "We hate hitting out of high rough, but you've got to look at what the tournament is trying to accomplish. They want the Canadian Open to mean something and hopefully the leader board looks like the leader board they want."

It wasn't short on former major winners.

Current Masters champion Charl Schwartzel (67) and former U.S. Open winner Geoff Ogilvy (68) were among seven players at 2-under, two strokes off the lead.

"Good players are playing well in this tournament," said Ogilvy, who wasn't a fan of the rough. "It's a quality looking leader board and at the end of the day that's all you can ask for. It doesn't really matter what people shoot."

Joining Ogilvy and Schwartzel at 2-under were Rickie Fowler (69), Jerry Kelly (67), first-round leader Kris Blanks (71), and Canadians David Hearn (68) and Adam Hadwin, a local playing on a sponsor's exemption who bogeyed 18 for a 66.

For the 23-year-old Hadwin, in his second year on the tier-3 Canadian Tour, the round was extra special because younger brother Kyle, who has had five major surgeries while battling Crohn's disease was able to leave a nearby hospital and walk the course. It was the first time since last year's Canadian Open, when Hadwin was the top Canadian, that Kyle was able to see his brother play in person.

Kyle wasn't able to travel when Adam qualified for this year's U.S. Open.

"He's a tough kid, he's been battling hard for a while," Hadwin said. "It's great that he's able to get out here and enjoy this with me."

Scott McCarron shot the lowest round of the tournament, a 65 that moved the veteran into a group of seven players at 1-under, and Tommy Gainey, who opened with a 77, matched it to move to 2-over and get below the 4-over cutline.

Despite no overnight rain to soften the course like early Thursday, scores were down by almost half a shot, but considering that first round was third-toughest on the PGA Tour this season at more than 3-over par, it was all relative.

Anthony Kim, coming off a tie for fifth at the British Open last week, was disqualified after signing for less than his 11-over 81.

"A.K. just got it going sideways a little bit and out here there's no faking it," said Fowler, who played with Kim and Lucas Glover, who is 1-under. "You've got to hit the ball in the fairway and stay out of trouble here."

The number of players under par was down — from 21 after Day One to 18 going into the weekend — and Campbell, Goydos, Fowler and Janzen were the only ones to stay under on both days as the thick rough claimed more than just scorecards.

Canadian favorite Weir, whose 2003 Masters win is a distant memory as he plummets to No. 475 in the world, withdrew after hitting out of the long rough and aggravating an elbow injury that cut short his 2010 season. Weir was 8-over after six holes when he pulled out.

"Very disappointing," he said. "This is our national championship. I want to play and have great fan support. But I'm just not going to re-injure it again. With this deep rough, I just can't hit it."

NOTES: Hadwin came the closest to the only bogey-free round of the tournament before his tee shot on 18 found the round and he took two shots to get out, making an 11-foot putt to save bogey. ... The scoring average Friday was 72.55 after being 73.02 on Thursday. ... Goydos, 47, would be the oldest winner in event history at almost two years older than Mart Calcavecchia, who won with a 5-under total the last time Shaughnessy hosted the event in 2005.