All-Star shortstop Javier Báez could return to the Chicago Cubs if they reach the playoffs.

Báez saw a hand specialist in Chicago who confirmed the slugger has a hairline fracture of his left thumb. He is expected to miss the rest of this month, but the team said Monday he will continue his rehab in hopes of playing in October.

The slumping Cubs headed into their series opener at San Diego in the NL's second wild-card slot.

Báez got hurt on a headfirst slide into second base during a 4-0 loss to Milwaukee on Sept. 1. He is batting .281 with 29 homers and 85 RBIs.

"We're just going to have to wait on Javy," manager Joe Maddon said.

With Báez and Addison Russell sidelined, touted prospect Nico Hoerner was promoted from Double-A Tennessee and got the start against the Padres.

The Cubs also recalled right-hander James Norwood from Triple-A Iowa. To make room for Hoerner on the 40-man roster, lefty Randy Rosario was designated for assignment.

Right-hander Adbert Alzolay was optioned to Class A South Bend after Sunday's loss at Milwaukee.

Russell was hit in the head by a pitch from Adrian Houser during the series finale against the Brewers. Maddon said the Cubs would know more about Russell's condition after he is seen by a local doctor.

The 22-year-old Hoerner was selected in the first round of last year's draft out of Stanford. He is the first member of the 2018 draft class to join a big league roster.

Hoerner hit .284 with three homers and 22 RBIs with Tennessee. He was limited to 70 games due to a broken left wrist.

He is the first Cubs prospect to make the jump from Double-A to the majors since Kyle Schwarber in 2015.

"The one thing that stands out about him is a lot of self-confidence," Maddon said. "Not in a braggart way, just a self-confident young man. From the moment I met him, he gave me the impression that he thought he belongs here, which I love.

"He's very comfortable in his own skin. I anticipate a good result. I know one thing, he's going to play hard and he thinks things through very well. He's one of those guys who has great makeup."

Maddon also said third baseman Kris Bryant, who had a cortisone shot in his sore right knee on Sunday, might be able to play Tuesday night.