Calcavecchia held a three-shot lead after 16 holes, but bogeyed the final two holes to finish with a 66. Frost, playing a bogey-free tournament, birdied No. 18 to also finish with a 66.
"I putted quite well yesterday and today," Frost said, casually sitting back in a chair.
"I'm glad there's no more holes because I'd probably bogey the next one too as (upset) as I am," Calcavecchia said. "Some days you leave the course happy, some days you don't. Today's one of those days where I'm not."
On the par-3 17th, Calcavecchia couldn't get up and down from the rough. His second shot on the par-5 18th -- which ranked as the day's second-easiest hole -- landed in a greenside bunker. His chip went about 75 feet past the hole and he three-putted from there.
"I hit four bad shots in two days and made four bogeys," he said. "It's getting old."
Playing with Calcavecchia for the second straight day, Frost made three birdies in a four-hole stretch on the front nine, before going six holes without another. He made two more in the final four holes.
"It was a day you had to think a little bit more than yesterday because the wind was coming at a little different angle. ... It was always across, especially on the back nine. It made it interesting," said Frost, who, like Calcavecchia, has yet to win on the Champions Tour.
Frost has five top-10s in his first full year on the tour, including a playoff loss at the Senior PGA Championship in May. Calcavecchia is playing in his fifth event after turning 50 on June 12.
Neither is putting extra pressure on themselves.
"You need to keep playing well week in and week out, and the win will take care of itself," said Frost, who noted that he beat Calcavecchia 9 and 8 in a 1977 junior tournament in South Africa the first time they met.
"His game hasn't changed over the years. He's been a great player because his putting has just been fabulous," Calcavecchia said. "He's got one of the purest strokes I've ever seen."
Cook, who tied for third at last week's U.S. Senior Open, shot a 5 under 67. He was 3 under on the front and made birdies at Nos. 13 and 14 to get within one shot of the lead, but he bogeyed No. 16.
Hanefeld was 4 under on the front, and birdied No. 10, 12, 16 and 18 on the back nine. He also has yet to make a bogey in the tournament, which has the potential to be his best ever. He has one top-25 in 10 starts this year, and his best finish in 52 career events is a fifth-place tie at The 2008 Principal Charity Classic.
"I just said to myself, 'There's really no reason I shouldn't be playing good again today.' I got off to a good start, nothing spectacular, and then I made a couple birdies and I said to myself 'There's a lot of birdies out here, I might as well try to make them."
First-round leader Tommy Armour III was just 1 under for the day, and was four shots back along with Mark O'Meara (66), who birdied seven of eight holes in one stretch, Ross Cochran (67) and Bruce Vaughan (67).
The openness of the TPC Twin Cities has been a welcome relief for tour players. The last two events were the British Senior Open in Scotland and the U.S. Senior Open at Sahalee Country Club outside Seattle, two unforgiving tracts were poor shots equaled poor results.
A few sprinkles fell on the course early in the day before humid conditions took over, further softening the greens and allowing players to continue taking aim directly at the pin. Forty-seven of the 78 players broke par, two more than Friday.
"If you don't have any elements to deal with these guys are going to go real deep," Hanefeld said. "The fairways are wide and the greens are fairly big so there's some room for error. There's a lot of birdies to be made, and you have to if you want to have a chance."
Defending champion Bernhard Langer knows he won't repeat. He is one of four players that is seven shots back.
"You need to be at least 10 under to have a chance," he said. No champion has defended his title in the event's 18-year history.