David Peterson Back in Rotation as Cubs Name Starters for Mariners Series

After a much-needed off day on Thursday, the Chicago Cubs will embark on a West Coast road trip that starts in the northwest.

The Seattle Mariners have left a lot to be desired this season and are currently 60-68. Unfortunately, though, this meant they did the Cubs no favors, handing the Milwaukee Brewers two wins in the last three days. This included a ridiculous 22-0 blowout loss on Tuesday night.

Maybe they can make it come to their second-straight NL Central opponent by forking over a series sweep! If one thing is for sure, the Cubs are set to have quite a strong trio on the mound.

Below are the projected starters for this weekend's slate!

Friday – Matthew Boyd

Aug 15, 2026; Chicago, Illinois, USA; Chicago Cubs starting pitcher Matthew Boyd (16) delivers a pitch against the St. Louis Cardinals during the first inning at Wrigley Field. Mandatory Credit: Kamil Krzaczynski-Imagn Images | IMAGN IMAGES via Reuters Connect

The Chicago Cubs will open their series against the Seattle Mariners with one of their most reliable arms on the mound.

Matthew Boyd is officially scheduled to pitch on Friday evening, and he is hoping to shake off one of his worst starts of the season. Against the St. Louis Cardinals, Boyd struggled with both his command and reducing hard contact. He allowed four home runs, which included three to Joshua Báez in his historic debut. Equally as troubling, he walked three batters for the second game in a row and had his fewest K's since June 30.

The big question now is whether this was just an off-day for a veteran arm or if it's a sign of what is to come for Boyd. His production since returning from injury would suggest it's the former. The sample size is large enough to feel good about his place in this rotation as the playoffs loom.

With that said, this should be a good get-right opportunity for him. The Mariners' offense has been disappointing all year, as they have just a .230 team batting average, which is the second-worst in MLB.

Saturday – David Peterson

Aug 12, 2026; Washington, District of Columbia, USA; Chicago Cubs starting pitcher David Peterson (19) pitches Washington Nationals during the first inning at Nationals Park. Mandatory Credit: Geoff Burke-Imagn Images | IMAGN IMAGES via Reuters Connect

Do you think David Peterson told Craig Counsell, "I told you so?"

The Chicago Cubs moved the former Mets southpaw to the bullpen in order to make room for Edward Cabera. It undoubtedly felt like a risky move. Sure, Cabrera was looking like his old swing-and-miss self during his rehab assignments, but his regular-season performance was subpar all year. The 5.10 ERA underscored that.

As for Peterson, he was looking completely rejuvenated in the Cubs' rotation. The ground ball pitcher had a 5-1 record and a 2.14 ERA in his six prior starts. All things considered, he was pitching like the exact kind of arm the Cubs want in front of their elite defense.

Nevertheless, Counsell made the move ... and he instantly regretted it. Cabrera went just 3.2 innings and let up 7 earned runs. The strikeout stuff that he flashed while rehabbing was nowhere to be seen. To make matters worse, he developed a blister during the game and was subsequently put on the IL.

All signs now point to this truly being Peterson's rotational spot to lose throughout the remainder of the regular season. If he does begin to struggle, perhaps we will see Cabrera return or Javier Assad get another shot. But it's likely going to take a lot for Counsell to make the change again.

By the way, this is also going to be the night that the Cubs face off against the top pitching prospect in baseball. So they really have to hope that Peterson keeps up the good work!

Sunday – Shota Imanaga

Aug 16, 2026; Chicago, Illinois, USA; Chicago Cubs pitcher Shota Imanaga (18) looks on from the dugout against the St. Louis Cardinals at Wrigley Field. Mandatory Credit: Patrick Gorski-Imagn Images | IMAGN IMAGES via Reuters Connect

Shota Imanaga shook off his three-homer game in epic fashion this week.

Facing off against the Chicago White Sox, another power-hitting squad, Imanaga looked like a juggernaut. He went 6.0 innings with only two hits allowed. To be sure, he did still allow 3 earned runs, but he also walked off the mound with 10 strikeouts and just a 1.09 WHIP.

Imanaga's chase rate now sits at 35.5 percent, which is in the league's 92nd percentile. His walk rate has also remained incredibly low, checking in at just 5.5 percent. Only the Angels and Guardians have a worse slug rate than the Mariners, and they have also struck out the eighth-most times this season. All good news for Imanaga!

Sign up for our free newsletter to stay up-to-date with all things Chicago Cubs.

Add us as a preferred source on Google