Initially, Garza planned to throw a bullpen session on Sunday to see how he felt. He never made it to the mound.
"It was more like positive hope," said Garza, who underwent an MRI on Monday that confirmed the damaged muscle behind his shoulder. "For a while it was deflating, disappointing. But I just had to take time and go look and evaluate where I'm at and just put a positive mind-set to it and come back stronger.
"I'm not afraid of work," he added. "It just wasn't what I was looking forward to the beginning of April."
Taylor Jungmann will pitch on regular rest in Garza's place on Wednesday against the Giants, and the Brewers will proceed with four starting pitchers through their weekend series against the Astros. Because of off-days, Milwaukee could actually opt to navigate its first 11 games with four starters before introducing a fifth arm on April 17 at Pittsburgh.
Zach Davies remains likely to be the first Minor League starter called up, manager Craig Counsell confirmed. Davies, who went 3-2 with a 3.71 ERA in six September starts for the Brewers, is scheduled to start Opening Day for Triple-A Colorado Springs on Thursday.
In the meantime, the Brewers will carry an extra reliever or position player. Tyler Cravy got the first shot to work out of the bullpen, called up when Garza hit the DL.
"I think Matt had a good spring. He had put himself in a good place to bounce back from 2015, so it's disappointing for him," Counsell said of Garza. "But it's four to six weeks, hopefully. Around the first week of May or second week of May, we'll have him back."
Garza, who plans to focus on lower-body strength during his DL stint, felt some discomfort before that troublesome outing in Houston.
"Just a little different soreness that I wasn't used to, but I was changing some stuff [mechanically], so I equated it to that," Garza said. "I guess it wasn't, and right now it [stinks]. But I've just got to get better and stronger and be here to support the guys. Just do whatever I can."