Harrison Bader to start rehab assignment, may join Yankees by Sept. 20

If all goes well, the Yankees may be able to dust off a new center fielder on Sept. 20.

Harrison Bader, who has not played a game with the Yankees since he was acquired from the Cardinals in the Jordan Montgomery trade, is expected to start a rehab assignment Sunday with Double-A Somerset.

Manager Aaron Boone said Bader, who has been out since late June with plantar fasciitis, will be Somerset’s designated hitter Sunday in Hartford, Conn., then will begin outfield work Tuesday.

“It’ll probably be at least a week,” the manager said Saturday before the Yankees beat the Rays, 10-3, in The Bronx. “But then if we get through that week, and the build-up is going fine, he could be in play when we start the homestand [Sept. 20 against the Pirates].”

Bader said there is “definitely discomfort” in his right foot, but he has been told he cannot further injure the foot by playing on it. The Yankees acquired the reigning NL Gold Glove center fielder knowing they would have to wait for Bader to get healthy, but they saw his defense as an eventual way to spell Aaron Judge in center.

The prolonged struggles of Aaron Hicks — and just about the entirety of the Yankees’ offense aside from Judge — makes any hitter welcome, even if Bader might not be ready yet.

“I’m not trying to get my timing back. I’m not trying to feel comfortable in the box,” said Bader, who posted a .673 OPS in 72 games with St. Louis. “I’m just trying to go and just understand that I can physically do something so I can come up here and play ball.”

Montgomery has gone 5-0 with a 1.45 ERA in seven starts for a Cardinals club that is running away with the NL Central. Bader, who said he only has been getting reps in center field, has had to watch his new club without being able to help.

“It’s definitely frustrating. I would say it’s more challenging than anything though,” said Bader, who was trying to find the bright side. “I’m happy that I now have a new set of tools to learn how to take care of my feet properly to make sure this never happens again.”

The Bronxville native has been a Yankee for nearly six weeks and has not been able to suit up, but he believes the wait will be over soon.

If he returns Sept. 20, he would have 16 regular season games left to make a difference.

“I couldn’t be more excited. I couldn’t be more positive,” the 28-year-old said. “I can’t wait to be in pinstripes finally. It’s been so long.”