The team will find out over the next two weeks. In Saturday's 15-7 loss to the Angels, Jeffress made a successful spring debut after missing the first two weeks of games because of a strained right hamstring and a stiff neck.
Jeffress pitched a perfect sixth inning, striking out the final two batters he faced while throwing a split-fingered fastball, an off-speed offering he hopes to feature more this year after tinkering with it during a breakthrough 2015 season. He followed Will Smith, who kept his spotless spring alive by working a scoreless fifth inning. Smith has yet to surrender a Cactus League run.
The two will open the season as co-closers, said manager Craig Counsell, who is open to either man claiming the role in time.
The mid-spring debut is reminiscent of Rodriguez, who never pitched more than nine Cactus League innings during his four springs in Brewers camp. As a closer, K-Rod's thinking went, he did not require the same building-up process as multi-inning pitchers.
Will the "K-Rod Model" ever be more widely embraced for late-inning specialists?
"We were talking about that, actually," Brewers manager Craig Counsell said. "Everybody is an individual, first of all. But I think you do it [pitch relievers from the start of] because if something happens in the middle of camp, they have [time] to get ready. You build in a little insurance by logging stuff early in camp.
"The example is, to me, Will has a base under him already. If something happens, he's OK. Jeremy has less of a base under him. Any setback, and then we'd be up against it pretty good."
Jeffress believes he has time to make six or seven appearances before Opening Day. His hamstring, he said, is back to full strength.
Chris Capuano, Taylor Jungmann, Corey Knebel, Jonathan Lucroy and Smith were among those in attendance Friday night at a Major League Baseball Players Association meeting in the Biltmore neighborhood of Phoenix. MLBPA executive director Tony Clark, who'd been in Brewers camp earlier in the day, briefed as many as 75 players, according to Knebel's estimate, on upcoming negotiations for a new Basic Agreement.
"It's as informed and engaged a group as I've ever been around, and my first year going to meetings and getting involved was 2003," said Capuano, a member of the union's Executive Board.
Capuano, who has a degree in economics from Duke University, has long served on the union's pension committee. This year he's serving on the negotiating committee.
Jones gets an inning
Right-hander Zack Jones made his long-awaited spring debut on Saturday in Minor League camp. The Rule 5 Draft pick had been sidelined by a sore shoulder.
The Brewers must keep Jones on the big league roster all season or offer him back to the Twins, so the next two weeks will be critical.
"He's a guy that's up against a little bit of a clock, for sure," Counsell said. "But still, he has to be healthy for six months, so otherwise it doesn't do us any good. Health still takes precedence."
• Scooter Gennett played second base for the first time on Saturday and called it a successful test of his right shoulder, flawlessly handling his one chance in the field. Arm soreness delayed his debut until Thursday, when Gennett had three hits as the designated hitter.
"It felt like normal baseball again," Gennett said. "No pain, no stiffness or anything like that."
• Counsell expects right fielder Domingo Santana to return to the lineup on Sunday after missing several days with stiffness in his left shoulder and neck. Santana was a full participant in drills on Saturday.
Adam McCalvy is a reporter for MLB.com. Follow him on Twitter @AdamMcCalvy, like him on Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.