Rose, the veteran Englishman, took the title on the first playoff hole in the Quicken Loans National at Congressional Country Club in Bethesda, Md., but Stefani took a huge step forward in his career.
"It was great to put myself in position, obviously in a playoff, to win a tournament," Stefani said after the tournament. "This is the first time I've been in that position coming in on Sunday late, and really happy about it."
With a 1-under 70 on the final day, Stefani finished 4-under par for the tournament, and that second-place finish earned him a spot in the British Open next month.
Stefani, a 32-year-old from the Houston area, began a sponsorship relationship with MLB.com in 2013, his first year on the PGA Tour after success on the Web.com Tour. A Lamar University product, Stefani gained some notoriety last summer with a hole-in-one in the U.S. Open -- and an ace of a reaction -- on the 17th hole at Merion Golf Club outside of Philadelphia.
As Sunday's round at Congressional wound down, Stefani matched Rose's final regulation score with a par on No. 18 after Rose had bogeyed it to lose a stroke. Stefani had birdied 16 but then bogeyed 17 before settling into the tie with Rose.
On the playoff hole, Stefani's tee shot on the par-4 18th went wide left and his second shot found the lake to the left of the green. He wound up with a double-bogey and Rose carded a par.
But on a day when leaders went plummeting down the leaderboard, Stefani stayed strong throughout the fourth round, one of only six players to shoot under par on the final day.
The result was his second top-10 finish of the season and the second top-5 spot as well. Stefani was fifth at the Shell Houston Open, his hometown tourney, earlier this season in a clutch performance -- he was on a minor medical extension of his Tour privileges, and the earnings at Houston earned him full exempt status on the Tour. In his rookie season in 2013, Stefani had two top-10 finishes.
The $702,000 check for second place at the National represents the biggest payday for Stefani, far surpassing the $256,000 he pulled in for his fifth-place finish at Houston.
Stefani entered the National ranked 155th in the FedEx Cup standings, and his second-place performance earned him 300 points, pushing him way up the ladder to 77th -- currently well within the top 125 that will compete in the season-ending playoffs.
Even though it didn't end up with a title, Stefani's performance at the National became the best of his career, one that bodes well for the future.
"Obviously it's a great experience to come out here and play and it definitely gives me the belief that I can win a golf tournament on the PGA Tour," Stefani said.