Blake birdied three of the final four holes for a 6-under 64 and a one-stroke lead Thursday in the Charles Schwab Cup Championship. Last year, he won at TPC Harding Park in San Francisco.
"It's been a long time since I've been able to defend a title," Blake said. "I have to admit I was nervous. I didn't know what to expect. I was just hoping to play well."
Couples is playing for the first time since a back injury forced him to withdraw during the first round of the Boeing Classic outside Seattle in late August. He completed a round for the first time since winning the Senior British Open in July for his second victory of the year.
"Beginner's luck," Couples joked after birdieing the final two holes on the Cochise Course. "I hit the ball solid. I'm thrilled to death to be 4 under."
"I'm very happy with my finish," Langer said.
Langer has a 211-point lead over Lehman and 657-point advantage over Chapman in the race for the $1 million annuity. The tournament winner will get 880 points, with players receiving a point for every $500 they earn in the $2.5 million event.
Langer and Lehman would win the season title with a victory, while Chapman needs a victory and some help to top the standings.
"Obviously, in the back of your head, there is always, 'What does everyone else do?"' Langer said. "But I can't control any of the other players."
The German star has two victories this season and leads the money list with $2,023,296. He's coming off a playoff loss to David Frost on Sunday in San Antonio.
Lehman, a Scottsdale resident, also has two victories this year.
"I'm disappointed with my scoring," Lehman said. "I misread a lot of putts and when you misread your putts you start to doubt your reads and the stroke sometimes follows suit. I think it's more about commitment, committing to a line and just rolling the putt."
The tournament is the 50-and-over tour's first in Arizona since the 2002 Tradition at Superstition Mountain. The Tradition, a Champions Tour major, was played on the Jack Nicklaus-designed Cochise Course from 1989-2001.
"The conditions are just beautiful," said Hallberg, a three-time PGA Tour winner who won his lone Champions Tour title in 2010. "I mean perfect lies in the fairways. You could really get the ball solid. But the greens are tricky. I think that's the defence of this course."
While Blake often plays similar desert courses in his hometown of St. George, Utah, he struggled with his distance control with shots flying farther because of the heat, low humidity and altitude at the mountainside layout.
"I drove it really well and the balls were going so far out there," Blake said. "The hard part right now for me to figure out is what iron shot, whether I need to hit a hard 8 or an easy 7. Sometimes, I hit a hard 8 and it goes 175 (yards). ... I feel like I'm making some bad swings on some of the irons because I'm a little leery of the distance it is going."
Blake won the Boeing Classic for his third career Champions Tour victory. He won his lone PGA Tour title in 1991.
"I've played well the last couple of months, the last few tournaments, so I had some confidence coming in," Blake said.