Alker finished strongly at the SAS Championship in North Carolina, carding an 8-under 64, including seven birdies and an eagle, in the final round to finish at 14-under for the tournament.
It extended Alker’s lead in the Charles Schwab Cup standings and took him to healthy earnings of $NZ5,237,105 this season.
He finished six shots behind American great Fred Couples, who turned back time to win his first tournament in 1939 days.
Couples (63) fired the lowest round of his Champions Tour career, a 12-under 60.
Couples was two shots behind Alker after four holes when the Hall of Famer went on a run that amazed even him. He ran off five straight birdies, made a key par on the 10th hole and finished with seven straight birdies.
"It feels really, really good," Couples said.
"I was talking to someone after yesterday’s round and I just said, you know, someone is going to shoot 65 or 66 and win.
"I warmed up on the range better than I’ve ever felt and I played really, really well. I did hit a crappy shot on 10 in the hazard and I made about a 30-footer (9m) for par, which was huge. Then I just started making putts."
Couples had not won since the American Family Insurance Championship in May 2017. The SAS Championship became his 14th victory on the Champions tour.
Couples averaged third in driving distance for the week and second in putts per green in regulation.
"It’s easy to say because we’re standing here, but I think it’s the best round I’ve ever played," Couples said.
"I hit a few loose shots, you know, got away from them, but I made so many putts."
Even with yesterday’s heroics, Couples said he would not play again this year, eschewing the Charles Schwab Cup Playoffs despite the fact the victory moved him from 60th to 34th in the standings.
"I’ll probably take the rest of this month off and then I’ll gradually start hitting a few in November, December. That’s normally when I do well because I live in California, the weather’s perfect. Once the season starts, I like to get off to a good start.
"This year my back was so bad, I really couldn’t even play until Augusta and I probably shouldn’t have played there, but I enjoyed playing there.
"This is my eighth tournament that I’ve played in, so that’s not very many."
Alker shot an even-par 72 on Saturday that left him in a tie for 40th.
But with 17 top-25s in 19 events this year, the in-form New Zealander always shaped as a threat in the closing rounds.
"It just got better as the week went on," Alker said.
"I started hitting the yardages and putting nicely, so it’s all come together. Good timing for the playoffs coming up, just got a lot of work to do."
Alker was left in awe of Couples’ performance.
"It’s sensational. Obviously Freddie just got it in the groove and has it rolling.
"You don’t shoot 12-under without putting well.
"Good on him. That’s fantastic, good to see."
