It was another one of the tour's biggest names who ended the day with a long putt to ensure Daley wouldn't have sole possession of the lead as he searches for his first tour victory.
Mark Calcavecchia holed a 50-foot birdie putt on No. 18 for a 6-under 64 on Saturday, moving him into a tie with Daley atop the leaderboard heading into the final round of the Senior Players Championship.
''Capping the day with a 50-footer on the last hole always helps,'' said Calcavecchia, who won the Montreal Championship last week. ''It always makes dinner taste a little bit better. ... All in all, I thought I played great.''
Calcavecchia's bogey-free round matched the best of the day and allowed him to match Daley at 12-under 198 at Fox Chapel. Daley, winless on the PGA Tour and Champions Tour, had a 68.
Lehman and Couples, the second-round leader and winner last year at Westchester Country Club in Harrison, N.Y., were a stroke back. Couples had a 70, and Lehman shot a 66. Lehman won the Regions Traditions in his last start.
After two consecutive days of temperatures in the mid-90s, the third round was played in slightly more bearable conditions.
Daley appeared as if he might wilt - not because of the weather but because of the pressure of playing in the first group with a pair of major tournament champions in Couples and Lehman.
Daley bogeyed Nos. 3 and 4 after Lehman and Couples each had already birdied No. 2. But Daley recovered with a birdie on No. 5 and avoided mistakes the rest of the way.
Currently with no status, a victory would ensure Daley a full exemption on the Champions Tour for a calendar year. The $405,000 first-place prize also would go a long way toward solidifying his place inside the top 30 on the final money list, which would earn him full status through 2013.
''This is a great opportunity for me,'' said a grinning Daley, who tied for fourth last month in the Senior PGA Championship. ''When you stay on that positive forward can-do page, things happen and it's good.''
Couples struggled with back problems, saying he felt ''horrible'' and that he was ''tired of feeling like this.''
Couples first had spasms while hitting out of the rough on the second hole, and the stiffness persisted throughout a round in which he was moving gingerly and had trouble bending over.
''I feel very badly for him and have a lot of empathy for him,'' Lehman said. ''He's the kind of guy that would never really talk much about it, but he hit a shot on the second hole and I think he almost went to his knees. And I think he really struggled the rest of the day.''
Still, Couples endured through the even-par round that kept him playing in the final group Sunday. Couples is attempting to join Arnold Palmer as the only player to successfully defend the title.
Palmer, from nearby Latrobe, won the tournament in 1984 and '85. He was on hand Saturday for the announcement of a youth golf endowment in his father's name.
''I just was really sore and couldn't get loose, but at the same time I'm one behind, so I'm in great shape,'' Couples said.
Jeff Freeman was 10 under after a 70, Fred Funk was another stroke back after a 64, and Bill Glasson was 8 under after a 68. Freeman needed only 11 putts on a back nine that featured four birdies and an eagle on 15. Funk eagled the par-5 third hole and had a stretch of five birdies over seven holes on the back nine.
After winning last week, Calcavecchia has progressively improved his score each day, opening with a 69 and shooting a 65 on Friday. The 1989 British Open champion has four top-five finishes in Champions Tour majors but has never won one.
Lehman extended his streak of rounds in the 60s to 11, which equals the third-longest streak of sub-70 rounds in Champions Tour history.
''I was really, really pleased with the way I played today,'' Lehman said. ''It was probably the best I've played of the three rounds so far.''