He drove the ball all afternoon, no hit more powerful than the one that ended the game in celebration.
"He scuffled a little bit early, trying to find his swing, getting a better feel for it, and I think you're seeing the guy we had last year who drove in a lot of runs and did a lot of good for us," said Twins manager Ron Gardenhire, who put Doumit fourth for Justin Morneau, who was out with flu-like symptoms.
This was the third blown save of the season for Wilhelmsen (0-1), all in his last four tries. The right-hander pitched a perfect ninth for the save Friday night, but he walked the first three batters he faced about 17 hours later after inheriting a 4-2 lead. Josh Willingham followed with a sacrifice fly, and Doumit -- who missed the cycle by a home run -- drove in two more for the walk-off win.
Doumit went 3 for 5 to raise his batting average from .218 to .230. He's 6 for 16 with one of each type of extra-base hit and six RBI in the last four games.
"Some guys get up there to try to get on base. Some guys get up there to try to do some damage. I was hitting cleanup today. I was up there to do some damage," Doumit said. "I was looking for one spot and a pitch I could drive, and I got it."
Wilhelmsen also issued two walks in a squandered save at San Diego on Wednesday. This one wiped out two homers by Jason Bay and an effective start by Aaron Harang. Wilhelmsen had two strikes on Doumit but threw him a fastball straight down the middle.
"The only strike I threw," he said, adding: "He knew it was coming and lit it up."
Joe Mauer rounded a wet infield from first base to slide into home for the winning run in the rain. Mariners manager Eric Wedge said he never considered removing Wilhelmsen, whose ERA jumped from 0.75 to 1.85.
"Closers, you live and die with them. He makes a pitch there and puts the ball on the ground? Game over. We win," Wedge said.
Rookie Caleb Thielbar (1-0) picked up his first major league victory with a scoreless ninth inning.
Four of Bay's eight home runs, all of them with no one on base, have been in his last five games. Kyle Seager also homered and scored after a single in the seventh.
Kevin Correia pitched into the seventh inning but gave up three home runs for the second straight start. After posting a 3-1 record and 2.23 ERA over five April appearances, the right-hander has been hit hard.
"Pick your poison. It's a lot quicker to give up two solo home runs than five base hits and two runs in an inning, so it's streaky. When I'm behind in the count, I've got to be a little bit more aware of throwing a better pitch," Correia said.
After Brian Dozier's two-out single tied the game at 2 in the bottom of the sixth for the Twins, Correia recorded two quick outs in the next inning before Bay drove a 2-1 breaking ball into the left-field seats. With Brian Duensing in the game, Raul Ibanez's single stretched the lead to 4-2.
Doumit played catcher for Mauer, who was the designated hitter.
"As far as I'm concerned he made three mistakes today, and that's good pitching," Doumit said of Correia. "He's kept us in games."
In his first season with the Mariners after injuries limited him to a career-low 70 games and a .165 batting average in 2012, Bay has sure rediscovered his power stroke this week. He hit 32 or more homers in three of five years from 2005-09 but went deep only 26 times for the Mets over the last three miserable seasons.
The Mariners have been struggling to find support in their rotation behind the dominant duo of Felix Hernandez and Hisashi Iwakuma, who shut out the Twins over 7 2/3 innings Friday night. But Harang has been sharp this week. He spun a four-hit shutout of San Diego at home Monday. This time, he allowed only four hits and two runs while striking out four. One of the runs was unearned.
- The Mariners have brought up RHP Jeremy Bonderman to start Sunday's game, which will mark the 30-year-old's first major league appearance since 2010. LHP Scott Diamond (3-4, 5.22), who is winless in his last four starts, will take his turn for the Twins.
- Of Wilhelmsen's 23 appearances, 19 have been scoreless. He has allowed 10 hits but 11 walks over 24 1/3 innings.
- Thielbar, a native of Randolph, Minn., about 40 miles south of Minneapolis, hasn't allowed a run in his first 7 1/3 innings.