Keegan Thompson struggles for second consecutive start, but Cubs win in 11

The Cubs’ pitching was a mess in August. The staff put up a 6.97 ERA last month, and the Cubs went 7-20.

During the last four weeks of the season, manager David Ross will be working to sort out the best roles for the Cubs’ young arms.

One of those is 26-year-old right-hander Keegan Thompson, who didn’t make it out of the second inning of the Cubs’ 6-5 walk-off victory Thursday against the Pirates after his second consecutive wobbly start.

‘‘It’s very frustrating,’’ Thompson said. ‘‘I’ve never really had issues throwing strikes. I was trying anything I could think of. I just couldn’t find anything.’’

Thompson said he felt as though his mechanics were off but declined to share specifics, saying he was going to spend the days before his next start dealing with what’s wrong.

‘‘Sometimes, I don’t know that there’s something that has to be off,’’ Ross said. ‘‘It’s something that he’s gotta figure out. He’s gotta be better, that’s the bottom line.’’

Pirates right-hander Mitch Keller kept the Cubs’ bats quiet through six scoreless innings, but they got to reliever Chad Kuhl in the seventh. The Cubs erased a three-run deficit in the inning by scoring five times on home runs by Rafael Ortega and Ian Happ. Happ has homered in four of his last seven games.

That lead lasted until the ninth, when Rowan Wick blew the save by giving up two runs. Wick allowed singles to Jacob Stallings and Wilmer Difo, and the Pirates loaded the bases on a catcher’s interference call against Robinson Chirinos. Pinch hitter Michael Perez then plated two runs with a single to right.

In the 11th, ghost runner Sergio Alcantara scored the winning run from third when Pirates second baseman Difo dropped Happ’s pop fly.

‘‘Wind can be tricky here,’’ Happ said. ‘‘High pop-ups like that, they can get a little crazy.’’

Thompson, who was making his third start since being recalled from Triple-A Iowa on Aug. 21, had pitched almost exclusively out of the bullpen for the Cubs in May, June and July and had been successful. He was optioned to Iowa on July 27 to stretch out his arm in preparation to join the rotation.

But if Thompson is going to factor into the Cubs’ rotation plans in the long term, this month is the time for him to work on the transition from reliever to starter. After giving up four earned runs in two-plus innings last Friday against the White Sox, Thompson said he thought he was dealing with some mechanical issues then, too.

Despite Thompson’s struggles, Ross said his ability to recognize what’s going wrong is a positive because Thompson can go to Cubs coaches for specific help.

‘‘That’s the great thing about players that know themselves and have those feelings and self-awareness of their body and control of their body,’’ Ross said. ‘‘When they bring that to a coach, we can immediately start diving into the information.

‘‘Let’s put some side-by-sides and videos and see where your hands are breaking, how fast you’re running through your delivery, different ways to tackle that.’’

Before the game, Ross said one of the things he would be watching for was whether Thompson’s velocity ticked back up from where it had been in his previous start. Ross said he hoped to see anything in the low 90s, and although Thompson sat in that range for most of his 54 pitches, he went as high as 94 mph.

Thompson ran into trouble in the first. He put Ben Gamel (walk) and Bryan Reynolds (single) on base with one out, then gave up a three-run homer to Colin Moran.

Thompson surrendered a two-out single to Difo later in the first, then walked Keller on five pitches to lead off the second. He struck out Cole Tucker and got Gamel to fly out after a mound visit, but when he gave up a two-out single to Reynolds, Ross decided Thompson’s night was done.

Figuring out what’s causing a pitcher such as Thompson to struggle as a starter after doing so well out of the bullpen means weeding through a lot of theories. Finding the right answer comes from examining all available information, Ross said.

‘‘We’ve looked at some pitching data, some mechanical stuff, some windup stuff from his earlier outings to his last one,’’ Ross said. ‘‘Maybe getting off his backside a little fast, getting a little bit taller, driving from the lower half . . . what the pregame routine looks like, how he’s meshing that compared to when he was coming out of the bullpen, just a lot of factors.’’

Thompson has pitched largely in relief in the majors this season, but he made the majority of his appearances as a starter in the minors and in college at Auburn. His struggles now might be a mix of late-season fatigue and mechanical issues, Ross said.

‘‘You just try to let them go out there, let them go through their routine, let them have their outing and compete and try to assess each and every time how to make them better,’’ Ross said.