Drew Smyly was cruising along in Game 2 of the Cubs’ doubleheader against the Brewers at Wrigley Field.

The veteran starter did not allow a hit in 3 innings, walking a single batter while throwing 49 pitches.

When Smyly came back out to start the 4th inning, manager David Ross was out near home plate, chatting with umpire Brian Knight. After a couple of warm-up pitches, Ross and Cubs trainer P.J. Mainville walked to the mound to chat with Smyly.

A few moments later, Smyly walked off the field with Mainville and Ross motioned to the bullpen. The team called it “right oblique soreness” for the southpaw.

“Right now, it’s just soreness,” Ross said. “We’ll get it looked at tomorrow. We’ll take some pictures of that stuff and see what we got.”

Ross said Smyly started feeling the oblique soreness towards the end of the 3rd inning but was able to finish that frame by striking out Andrew McCutchen.

As Smyly left, Anderson Espinoza trotted out to the mound to make his MLB debut in relief. Espinoza was called up to the majors from Double-A Tennessee ahead of Monday’s doubleheader.

Smyly’s injury comes at a bad time for the Cubs, who had to place fellow veteran starter Wade Miley on the IL Sunday morning.

In addition, the Cubs also added outfielder Seiya Suzuki and infielder Jonathan Villar to the IL Monday.

“We’ve got some guys banged up right now for sure,” Ross said.

Smyly — who signed as a free agent during Spring Training — has a 3.80 ERA in 42.2 innings this season.

The Cubs are in the midst of a brutal stretch of the schedule that features 11 games in 9 days before their next off-day on June 6. That includes Monday’s doubleheader and another double dip on Saturday against the Cardinals.