Mahan is reserved and unassuming, Fowler tends toward the flamboyant.
The quiet one prevailed, barely, at the Phoenix Open.
Mahan defeated the younger Fowler by a stroke on Sunday for his second PGA Tour victory. For now, Fowler will have to settle for another second close call in Arizona.
The 27-year-old Mahan had an eagle and a pair of birdies in a late four-hole span to finish at 16-under 268. Mahan, whose first victory came at the 2007 Travelers Championship, closed with two bogey-free 6-under 65s.
Fowler, just 21 and a tour rookie, had a final-round 68 for the second runner-up finish of his young career, both of them in Arizona.
In his second PGA Tour event last Oct. 25, Fowler lost in a three-way playoff to Troy Matteson in the Frys.com Open just down the road at the Grayhawk Golf Club.
"Been in a playoff and having a putt to go into the playoffs," Fowler said, "so obviously I'm going to try to play out here as much as I can."
Mahan and Fowler barely know each other, but they are Cowboys through and through.
"Oklahoma State has had a lot of great players, and they keep putting them out there it seems like every year," Mahan said. "Rickie is a great player and a great kid. I'm proud to call him a Cowboy."
Added Fowler, "It's always a little better to lose to a Cowboy."
South Korea's Y.E. Yang also shot a 65 to finish at 14 under, two off the pace. Last year's PGA Championship winner, Yang led until his tee shot went in the water at No. 17.
Mathew Goggin, Chris Couch and Charles Howell III tied for fourth at 13 under.
Third-round leader Brandt Snedeker struggled mightily with a 78 to wind up far back at 7 under.
The win was worth $1.08 million.
Although he hadn't won, Mahan has played well the past two years. He played on the 2008 Ryder Cup team and had six top-10s in 2009, including a runner-up finish at the AT&T National. His earnings the last two years topped $5 million.
"It's just finding a way to win. I just haven't been able to do it," he said. "So obviously it feels great to get off the year on my fifth tournament to win. It gives me a lot of confidence in myself that I'm doing the right things in my game, and it feels great, it really does."
A total of 0.67 inches of rain fell and wind reached 47 mph overnight at TPC Scottsdale and sprinkles lingered Sunday morning. But the rain subsided by the time the leaders teed off at noon.
The tournament, in its 75th year, was known as the FBR Open but returned to its longtime Phoenix Open name when Waste Management Inc. took over as the title sponsor this year.
The weather held the estimated final-round crowd to just under 44,000, well off last year's 60,000-plus. That brought the week's total attendance to nearly 426,000, down from 470,000 a year ago at the rowdy event that always draws the biggest crowds on the tour.
Mahan hit his second shot on the par-5 13th 250 yards within 7 feet of the pin and made the eagle putt to reach 14 under.
His 18-foot birdie putt on the par-4 14th moved him to 15 under.
The clincher came at the notorious 16th, the par 3 surrounded by bleachers filled with noisy, irreverent fans who cheer and boo with equal enthusiasm.
Mahan's tee shot caught the edge of the green and he made the subsequent 14½-foot putt to regain the lead at 16 under.
"You still have a tournament to win, you can't really worry about the people," he said. "You just kind of have to block it out, but at the same time kind of enjoy it because you don't have that opportunity to have so many people watching you on one hole."
At the 15th, the open desert course's final par 5, Fowler chose to play conservative and lay his shot up rather than go for the green, which is surrounded by water. He said he felt he was a bit too far away from the pin to go for it, considering he was just one shot back and had what he felt were good birdie chances on Nos. 16 and 17.
"I felt that instead of bringing trouble into play," Fowler said, " ... I took the safe route."