David Ross isn’t in the business of playing what ifs.

He can’t plan as if Marcus Stroman — who suffered a right rib cartilage fracture and has no timetable for a return — will be back at some point in the middle of September.

“We’re doing none of that,” the Cubs manager said. “It’s like Brad Boxberger and Nick Burdi, we’ll have to wait till they’re ready and see if they can help us and all those things. He’s been an important part of our success when he’s healthy and it stinks, bad news, but we’ll continue on.

“This game moves on.”

Stroman’s absence creates another void for a rotation that can’t afford many more setbacks.

In the immediate aftermath, that means Javier Assad — who has been stellar over the last two months — steps into the rotation.  The rookie has a 1.29 ERA and 0.97 WHIP since June 16 across 12 games and 2 starts. In that time, he’s served as a long reliever, a leverage arm against the Cardinals and now on the starting staff.

“Assad has been fantastic for us in all these different roles,” Cubs president of baseball operations Jed Hoyer said.

But that still leaves one opening in the rotation. The Cubs are using Jameson Taillon, Justin Steele and Kyle Hendricks — in that order — against the Royals this weekend. That means Assad likely starts Monday in Detroit and the Cubs will need a starter for the second game against the Tigers and somebody to serve as the fifth man in the rotation.

“It’ll be [Drew] Smyly or Hayden [Wesneski] that’ll slide into that,” Ross said in speaking of the fifth starter spot. “I’m probably leaning Smyly pretty heavily to make those starts. But we’ll get through the off day tomorrow and kinda reassess some things.”

Smyly pitched the 9th inning on Wednesday, striking out two and allowing a single. He was just recently moved to the bullpen amidst his struggles as a starter. In 11 starts since May 28, Smyly has a 7.45 ERA and 1.80 WHIP.

The Cubs opted to move him into a reliever role while he worked through his struggles — something that also gave Ross a lefty in the bullpen. But with Stroman’s injury, Smyly might find himself back in the rotation. Smyly has struggled against lefties — they have a .965 OPS against him this season compared to .769 against righties. The Cubs were hopeful that the move to relief could help the veteran southpaw rediscover his groove.  

Meanwhile, Wesneski has had his own struggles against lefties — they have a 1.032 OPS against him. He’s served as a long-relief option at various points this season, so keeping him in that role while moving Smyly to the rotation creates some comfort level for each.

The shuffling around of Smyly or Wesneski has some ripple effects on the Cubs’ bullpen, which has been stellar of late. The relief corps has been at their best when there’s a long-relief option to cover innings or bridge the game — such as the role Assad filled before being shifted into the rotation. 

The Cubs have a pair of length options in the bullpen right now — Michael Rucker started in his final outing at Triple-A Iowa and threw 60 pitches in 3 innings — so the Cubs can quickly pivot to Rucker or Wesneski if they need length before turning it over to their leverage arms of Michael Fulmer, Julian Merryweather, Mark Leiter Jr. and Adbert Alzolay. 

“We’re gonna have to have Rucker step up, [Daniel] Palencia step up,” Ross said. “Hayden can take the ball for some length down there. Who knows? If guys aren’t performing, there’s guys in the minor leagues waiting for their opportunity to help as well. This is why it’s important to have really good pitching and depth throughout your organization and guys continue to get better and grow.

“It’s never just one guy or three guys and the back end.”