(CBS) As he recovers from a grade one hamstring strain, Cubs right-hander Jake Arrieta will throw a bullpen session later Thursday, a simulated game in the coming days and then plans to be back on the mound for game action “as soon as possible,” he told the Bernstein and Goff Show on 670 The Score.

“I’ve been making a lot of progress,” Arrieta said. “I’m feeling good. Everything is pointing in the right direction.

“The biggest part of the progression is kind of pushing it to the point where there’s no discomfort, no pain and controlling the effort that way, just so you’re not taking any steps back. And up until this point, we’ve been able to do that. We’ve been able to kind of push it without going overboard, and that’s really the biggest part of the rehab process, trying to make strides without having any setbacks. That’s kind of where we’re at now. I feel really good about it. It’s just been for me personally trying not to do too much too soon.”

Arrieta has been dominant in the second half, going 6-2 with a 1.98 ERA while holding opposing batters to a .198 average. He’s 14-9 with a 3.48 ERA on the season.

“It could’ve been worse, definitely,” Arrieta said of his injury.

Jen-Ho Tseng is taking Arrieta’s turn in the rotation Thursday when he makes his big league debut against the Mets. The Cubs chose to give him the ball so they could send left-hander Mike Montgomery back to the bullpen and strengthen it.

Entering play Thursday, Chicago led Milwaukee by 2.5 games in the NL Central and St. Louis by three games.