MILWAUKEE — The Cubs traded for a left-hander to add to their bullpen Friday, but the bigger roster news five days before the trade deadline involved the veteran hitter they’ve sought since early May.

Former World Series MVP Ben Zobrist plans to return from personal leave for the September stretch drive, team president Theo Epstein said before the Cubs lost 3-2 to the Brewers in the opener of a three-game series.

Zobrist, who has been on the restricted list since May 8 dealing with family issues related to a pending divorce, has been working out, including baseball activities, Epstein said, and could begin playing in what amounts to minor-league rehab games by next weekend.

“He’s still figuring out exactly when he’ll be ready, but he’s working out, and he’s been getting mentally ready,” Epstein said. “We’re excited that he’s going to give us everything that he has to try to come back and help the team down the stretch and hopefully into October.”

The Cubs remain active in trying to shore up bullpen and bench depth before the deadline Wednesday, but a successful and healthy return of Zobrist would go a long way toward navigating the final kick of the tightest division race in the majors.

“We hope to have great depth, and he’ll be a big part of that,” Epstein said. “But it’s not something we’re going to hang our hat on and say our position-player mix is completely settled because Ben’s going to attempt to come back for us.”

Having already signed closer Craig Kimbrel to a three-year, $43 million deal last month, the Cubs traded for catcher Martin Maldonado on July 15, and on Friday traded for Giants left-hander Derek Holland as a short-relief weapon against left-handed hitters, who are hitting .182 against him this year with only one extra-base hit.

And they’re not done trying to add depth, even as Epstein pointed optimistically at some right-handed pitching and position-player depth at Class AAA Iowa — and all but dismissed the idea of any kind of blockbuster deal.

“We had to dig really deep and get really creative financially to make [the Kimbrel deal] happen,” he said. “So as we look at the totality of what we’ve done, we are factoring that in, too.

“I’m not trying to lower expectations or lower the bar for what we’re trying to accomplish, but that did eat up a lot, if not basically all of, our financial flexibility and address a real need.”

In fact, the Cubs only had the flexibility to sign Kimbrel because of Zobrist’s prolonged absence, which could mean almost $8 million in recouped payroll by the time he returns from the restricted list.

Zobrist, 38, will be allowed up to 30 days of minor-league games to prepare for a return from the restricted list. He must be

reinstated before Sept. 1 to be eligible for the postseason roster.

Zobrist started slow this season before leaving the team (.241 with a .596 OPS). But he hit a career-high .305 last year with an .817 OPS.

“We’re thrilled by this news, happy for him, happy for us, and we understand there’s still a lot of steps that have to happen,” said Epstein, who has been in regular contact with Zobrist. “He’s not one to take this lightly. And if he can’t play at a high level, he’s not going to try to fool anybody, that’s for sure.”