During that stretch he tended bar at The Hut, a watering hole by the University of Arizona in Tucson, Ariz., his hometown. He hiked national parks in the West and Southwest. He backpacked across Europe.
"He was a free spirit. I thought of him as a sort of displaced hippie," said Doug Finical, co-owner of The Hut.
In three years, the then-former pitcher served pitchers of beer and every kind of drink imaginable, including the bar's specialty, the Fat Man -- 60 ounces of rum and tropical juices named in honor of the first atom bomb.
Mariners pitching coach Carl Willis observed, "Sometimes when you're young, you're unsure of what you really want to do. He was unsure and had the confidence enough to step away, and then he decided, 'Hey, baseball's what I want to do.'"
That was in 2009, at age 26, six years after the Brewers had suspended him for a year for twice testing positive for smoking pot. It suddenly dawned on Wilhelmsen as he watched a big league game on TV that his life was on the wrong track.
"What the hell am I doing?" he shouted to himself. He quit smoking, got back into shape, made the Tucson Toros roster and pitched in relief in 11 games for the independent Golden Baseball League team -- and married Cassie Bowden, his high school sweetheart.
Wilhelmsen tweaked his arm late in the season, and when the Brewers, who had drafted him in the seventh round out of high school in 2002, relinquished his rights, the Mariners signed him.
He worked his way up their Minor League system in 2010, was on Seattle's Opening Day roster in 2011 and made his big league debut three games into the season with one mop-up inning (no hits, one strikeout) in a 7-1 loss at Oakland.
"I did a lot of climbing in a hurry," he said.
Interesting choice of words. During those years away from the game, Wilhelmsen reconnected with Cassie. They hiked through national parks in Arizona, Utah, New Mexico, California and Oregon.
Then they backpacked through Amsterdam, Cologne, Munich -- "Oktoberfest, that was a blast!" -- Florence, Venice and Rome, Nice and Paris and London. "No climbing," Wilhelmsen said. "Just the western European tourist sites, museums. This was my wife's part of the trip, the educational part."
When the Brewers suspended him before he put his baseball career on what he thought would be permanent hold, "I wasn't mentally prepared for professional baseball," Wilhelmsen said. "I didn't have the love for it that you need to go far in this game. I was just a kid and I wasn't ready to grow up yet."
But in 2009, "I just started getting serious about life. I started thinking about the future, which I wasn't doing when I was 18, 19, 20, 21. I didn't want to come home at 4 in the morning smelling of beer."
Ultimately, his agent Steve Canter got in touch with Jack Zduriencik, who had been Milwaukee's scouting director when Wilhelmsen pitched there and had become the Mariners' general manager.
"He decided to bring me on up and see what I had, and I guess he liked what he saw," Wilhelmsen said. "It went pretty quickly after that."
Bruce Lowitt is a freelance writer based in Tampa, Fla.