Dufner's nine-under 63 came from eight birdies, an eagle and one bogey.
OAKVILLE, Ontario (AP) -- Jason Dufner threatened to shoot in the 50s, then settled for a 9-under 63. Mark Calcavecchia made a PGA Tour-record nine straight birdies. And there were two more aces in perfect scoring conditions at the rainy Canadian Open.
Soon after Dufner finished the second round in light rain Saturday, heavy showers hit the already-saturated Glen Abbey course, forcing tour officials to postpone the third round until Sunday morning.
Dufner eagled the par-5 13th to reach 9 under for the round, but played the final five holes in even par -- birdieing the par-5 16th, dropping a stroke on the par-4 17th and saving par on the par-5 18th after hitting into the water.
"I played very well, hit a lot of fairways, a lot of greens. Made a couple more putts today," Dufner said. "It started raining at the end, conditions got a little tougher, but 63 is a pretty good score, and leading after two rounds is always great."
At 13 under at softened Glen Abbey, Dufner had a one-stroke advantage over Jerry Kelly (67) and 2001 winner Scott Verplank (67). Nathan Green (65), Peter Tomasulo (68), Martin Laird (69), Pat Perez (67), Camilo Villegas (71), Bob Estes (67), Retief Goosen (69) and Kevin Na (71) were 10 under.
Unable to finish the second round Friday night before lightning forced the suspension of play, Kelly returned Saturday to play the final three holes.
"I don't think they've got the mowers out there as heavily as they'd like to, so it's getting a little hairy out there," Kelly said.
Calcavecchia opened the delayed second round with two pars, then reeled off nine straight birdies. His nine birdie putts were from 15 feet or closer. With 15-year-old son Eric working as his caddie, Calcavecchia shot a 65 to reach 8 under.
"It's just fly it right to the stick," Calcavecchia said. "You give the guys out here no wind and greens that are plugging, you're going to see a lot of low scores."
Calcavecchia broke the record set by Bob Goalby in his 1961 St. Petersburg Open victory and matched by Fuzzy Zoeller (1976 Quad Cities Open), Dewey Arnette (1987 Buick Open), Edward Fryatt (2000 Doral-Ryder Open), J.P. Hayes (2002 Bob Hope Classic) and Kelly (2003 Las Vegas Invitational).
The streak ended on the par-4 third when the 49-year-old player's chip from over the green went 5 feet past. He saved par to remain 10 under, but dropped a stroke on the par-3 fourth after hitting into a greenside bunker, and bogeyed No. 8.
"I think adrenaline kicked in a little bit, even more than it already was," said Calcavecchia, the 2005 winner at Shaughnessey in Vancouver, British Columbia.
Leif Olson and Casey Wittenberg had holes-in-one on the par-3 15th, the fourth aces of the round on the 132-yard hole -- and the only ones on the hole in 25 Canadian Opens at the course. Olson's ball caromed off playing partner Kris Blanks' ball. All four players won 2009 BMW Z4 Roadsters.
There have been six aces overall, the most since the tour began keeping extensive records in 1971. There were five in the 2004 John Deere Classic.
Canadians Mike Weir (66) and Stephen Ames (69) were 7 under. Pat Fletcher was the last Canadian winner, taking the 1954 event at Point Grey in Vancouver.
Weir was back on the course for the first time since opening with a 71 on Thursday in a round delayed 7½ hours because of rain.
"This has been such a crazy week," Weir said. "At least today, I was able to play 18 holes and actually get in some kind of a rhythm."
Former Southern California player Jamie Lovemark, making his pro debut, followed an opening 74 with a 66 to finish at 4 under.