David Frost waves to the fans after sinking his putt on the 15th hole during the second round of the Toshiba Classic on Saturday. (SCOTT SMELTZER, Daily Pilot / March 16, 2013)

NEWPORT BEACH — If the second round is any indication of what to expect from David Frost and Fred Couples on Sunday, then the final round at the 19th Toshiba Classic should be one to watch. Or as Frost said, "it will be a fun day."

Frost sank a 15-foot eagle putt on No. 18 to carry a one-shot lead against Couples, who has a strong backing from fans at Newport Beach Country Club.

"It was a day when Freddy and I battled it out," said Frost, a 10-time PGA Tour winner who's had six top-10 finishes in his past six events on the Champions Tour. "We were on top of the leaderboard all day."

Frost shot a 5-under-par 66 and is at 13 under par after two rounds. Couples also shot a 66. Jim Gallagher Jr., who needs a win to remain exempt on the Champions Tour, is in third at eight under after carding a 68.

Couples, a 15-time PGA Tour winner highlighted by his 1992 Masters victory, just missed on a 35-foot putt for eagle on No. 18 and settled for a two-foot birdie putt, opening the door for Frost.

The 53-year-old South African usually responded well against Couples on Saturday. Each time Couples sank birdie putts on 10, 12 and 15, Frost followed with three birdies of his own.

"I know I'm going to see from him it's going to be good golf," said Couples, an eight-time winner on the Champions Tour, including here in 2010. "He's one ahead. I'm certainly not going to be able to shoot a 69 or 70 and win. I gotta shoot something very, very good, maybe like [Saturday]. He's going to play well and I think I will, too."

In addition to his eagle, Frost collected four birdies, three on the back nine, and one bogey.

Couples, 53, said he didn't play as well as his first round when he shot a 64. He had three birdies on the front nine, but the front also included two bogeys. He made up for it with four birdies on the back nine.

"It's so challenging playing with a guy like Fred," Frost said, "because a lot of times he putts first … and I keep saying to myself, he's going to make this, he's going to make this, and lo and behold, he makes it.  And then I have to kind of keep my composure, and fortunately for me I made a couple birdies on top of where he made birdies.  And it's really a fun challenge and that's what we actually live for.  We live for the moment of getting in the heat of the battle like this, and you don't want to get scared and run away from it, you know.  Just like you don't have to really approach it as if it's the moment. You just try and play your game."

Couples says he feels healthy and has been trying to stay loose with extensive hitting, mostly with his wedge, on the practice range. The cold temperatures can be challenging on his troublesome back. He's trying to become just the second golfer to win twice at the Toshiba Classic.

"I haven't played a whole lot," said Couples, who lived in Newport Beach for a few years in the 1980s. "I practiced the last three or four days before I came here in Palm Springs, and [now] it's a lot cooler and I'm a lot tighter, so I'm not hitting drivers that's for sure. But I'm hitting a few more wedges."

Scott Hoch shot 64, the low for the second round and his career best on the Champions Tour. He's at seven under, tied for seventh with Jay Haas, Bob Tway and D.A. Weibring.

Esteban Toledo, an Irvine resident and a former NBCC honorary member, shot 68 to match his first-round score and is tied for eighth with Dan Forsman and Peter Senior.

Hall of Famer Tom Watson shot 67 and is tied for 11th with Fred Funk and Bernhard Langer, the 2008 Toshiba Classic champion.

steve.virgen@latimes.com

Twitter: @SteveVirgen