Garza completed a four-year contract with Milwaukee on Sunday, strengthening the top of the rotation and boosting the Brewers' hopes following a disappointing season.
The team made the announcement, saying the contract included a vesting option for 2018. Earlier in the afternoon, team owner Mark Attanasio was on stage during a question-and-answer session at a fan event and said a deal was in place.
General manager Doug Melvin called Garza an "established, top-of-the-rotation pitcher."
"The thing about signing Matt now, it gives us a lot more depth and, as you know, during a baseball season, you never use five starters," Melvin said. "So, just kind of wait and see how spring training unfolds, and always having the available depth is important to stay in a 162-game season."
A person familiar with the negotiations, who was not authorized to speak publicly about the contract, told The Associated Press the deal was worth $50 million with an extra $1 million per year available in reasonable performance bonuses for a starter.
The 30-year-old righty went 10-6 with a 3.82 ERA last season for the Chicago Cubs and Texas Rangers. He missed most of the first two months while recovering from an injury that affected his side and back.
Garza will join Yovani Gallardo and Kyle Lohse as Milwaukee's top starters. He is 67-67 with a 3.84 ERA in eight seasons with Minnesota, Tampa Bay, the Cubs and Texas.
The Brewers ranked ninth in the National League with a 3.84 ERA last season, when they finished fourth in the NL Central at 74-88.
Garza was looking forward to pitching—and hitting—in the NL Central again.
"It's fun. I like the Central, I like pitching in the Central," he said on a conference call. "I like swinging the bat in the big parks."
The move also adds depth to Milwaukee's staff and puts less pressure on young pitchers such as Wily Peralta and Tyler Thornburg at the back end of the rotation.
Milwaukee also has Marco Estrada and Johnny Hellweg as rotation options, and lefty Will Smith was acquired from Kansas City in December for outfielder Norichika Aoki.
"We've said now for a couple of years that we're focusing on pitching and pitching depth," Attanasio told reporters. "You can never have enough pitching depth, and I would argue we have as much pitching depth as we've had (in) my 10 seasons of ownership."
Garza was the MVP of the 2008 AL championship series for Tampa Bay, beating Boston twice. He also has thrown the only no-hitter in Rays history, on July 26, 2010, against Detroit.
His agreement with Milwaukee was reported last week—but the Brewers were a bit of a surprise suitor for Garza's services. The team issued a statement Thursday that it was in talks with Garza but hadn't reached a deal at that point.
"These deals can go to the 11th hour and then not come together," Attanasio said. "So you don't know until you know."
Follow Genaro Armas at http://twitter.com/GArmasAP