CHICAGO — Pittsburgh Pirates ace Gerrit Cole expressed confidence he’ll return this season after returning to the team and playing catch Tuesday.

Cole was placed on the 15-day disabled list Monday and traveled to Los Angeles for a second opinion with a specialist, who confirmed posterior elbow inflammation.

“This is very encouraging news,” Pirates trainer Todd Tomczyk said. “He is now focused on how he is going to help this team win some ballgames the rest of the season.”

Pittsburgh entered Tuesday night’s game against the Cubs 1 1/2 games behind St. Louis for the second NL wild card.

Cole, 7-9 with a 3.55 ERA in 20 starts, played catch in right field with Tomczyk before Tuesday’s game as pitching coach Ray Searage looked on.

“It’s comforting to have confirmation that you’ll be OK,” Cole said.

Cole is on the DL retroactive to last Thursday, meaning he is eligible to return Sept. 9.

Cole had a 6.08 ERA in five August starts and said he alerted the team of a “level of discomfort that was concerning” after allowing five runs and seven hits in five innings last Wednesday against Houston.

Tomczyk said it’s uncertain how Cole was injured. He missed time in spring training with sore ribs and spent more than a month on the disabled list earlier this season with a strained right triceps.

“That is an ongoing discussion. He did have a slow start to the season with the rib injury,” Tomczyk said. “That could be a factor. And there’s the assumed risk of throwing a baseball.”

Cole’s absence means all five starters from the beginning of the season are no longer in Pittsburgh’s rotation. Yet the Pirates remain in the thick of the playoff race.

“It’s like coming back from a road trip and your wife has rearranged the furniture,” manager Clint Hurdle said. “After you bump your shin a couple times, you’ve got to find a different way to cross the living room.

“We’ve had to find a different way to get across the room this year. And it’s been a really good opportunity to learn.”