Jason Dufner, Jerry Kelly, Jeff Overton and Anirban Lahiri had the lowest scores in the first round of the CareerBuilder Challenge. Adam Hadwin had as good of a round, if not better.

Hadwin opened with a 6-under 66 on Thursday on PGA West's TPC Stadium Course, a number that left the Canadian two strokes back on the leaderboard — and two shots ahead of what he would have taken entering the day.

"You give me 68, I probably would have walked away and not played today," Hadwin said. "So, 66 bogey-free is a fantastic start."

Ryan Palmer, Rhein Gibson and Si Woo Kim, at 67, were the only other players in the top 31 on the leaderboard who opened on the difficult course that is back in the tournament rotation after being dropped following its 1987 debut. It had a stroke average of 71.825 in perfect conditions, while the adjacent Nicklaus Tournament Course averaged 69.424, and La Quinta Country Club 69.596.

Hadwin birdied the par-5 16th, avoiding the 20-foot deep bunker on the left side of the green, and finished with pars on the island-green 17th and water-guarded 18th.

"I played Q-school here, so I got a pretty good feeling the way the golf courses play," Hadwin said. "You have to get yourself around without making some big mistakes. ... You got par 5s with water that you try and be too aggressive, you can easily make a 6 or 7 and that's going to throw you pretty far back."

Also the site of the final round Sunday, the Pete Dye-designed course finally got another chance this year out of necessity when PGA West's Palmer and Nicklaus private layouts dropped out.

"Visually, it's a much more intimidating golf course off the tee," Hadwin said.

Phil Mickelson opened with 68 at La Quinta in his first start since the Presidents Cup in October, playing a seven-hole stretch in 6 under. The 2002 and 2004 champion is winless since the 2013 British Open.

"I've had a lot of time off," Mickelson said. "It was fun to get back into the swing of it. We had a beautiful day here. Weather's spectacular. Golf course was great. I had a good solid round."

Lefty holed out for eagle on the par-4 eighth with a shot that spun back 15 feet, chipped in on the next hole for a front-nine 31 and added another birdie on 11. He three-putted for par on the par-5 13th and made two late bogeys. The round also was the 45-year-old Mickelson's first since splitting with swing coach Butch Harmon to work with Andrew Getson.

"I felt good with my game," Mickelson said. "I didn't feel like I was fighting it. I was able to kind of let it go. I didn't hit a lot of shots really close, I just hit it kind of OK. Didn't putt great. But I had a couple shots that I holed out."

The 49-year-old Kelly had two eagles at La Quinta.

"In the past, this has been the tough golf course," Kelly said. "So, it was strange just how the mindset changes when this becomes the so-called easier one and you have to get it."

Dufner and Overton opened on the Nicklaus course, and Lahiri played at La Quinta, the lone holdover in the three-course lineup. Dufner prepared for the new venues before going to Hawaii for the Sony Open.

"I came out before I went to Sony and played these golf courses, both of them, twice," Dufner said.

Lahiri, from India, played last week in Malaysia in the EurAsia Cup matches.

"Obviously, still feeling all the travel from coming from Asia, but really happy with the way I hit the ball," Lahiri said. "I don't think I missed a green all day."

Defending champion Bill Haas had a 66 at La Quinta. He eagled the par-4 first hole.

"Ball-striking, I think I left a lot of room for improvement, which is a good sign," said Haas, also the 2010 winner.

DIVOTS: CareerBuilder is in its first year as the title sponsor of the event long called the Bob Hope Classic, taking over for Humana. ... Patrick Reed, the 2014 winner, had a 69 at La Quinta. ... British Open champion Zach Johnson shot a 73 at La Quinta.