PITTSBURGH -- Chicago Cubs pitching coach Chris Bosio recently revealed that the skin problem starter Jake Arrieta has had around his pitching thumb goes back several months -- and has affected Arrieta's performance during that time.

Arrieta will try to battle through the issue again on Saturday night as he takes the mound against the Pirates with a 6-4 record and 4.68 ERA.

“It goes all the way back to spring training,” Bosio said Friday afternoon. “It was just a lingering thing that never went away, and it’s progressively gotten worse.”

The ailment revolves around open skin around the right-hander's thumb, which has been tender for some time. The injury worsened before his most recent start, six days ago, and prevented him from throwing between outings. Arrieta failed to get out of the fifth inning against the Colorado Rockies on Sunday after being staked to a 4-0 lead in the first-inning. He lost his command in the fifth inning, which can happen after not throwing between starts.

But in Arrieta’s case, it actually could have a good effect, according to Cubs manager Joe Maddon.

“Pitching as much as they have the last couple of years, to really curtail what you do between starts is not a bad thing,” Maddon explained. “I’ve seen guys not lose command, and actually gain command, because they feel strong and fresh when they get to the game situation.”

Arrieta often doesn’t throw full bullpen sessions between starts as innings pile up later in the season, but with his rocky start to the 2017 campaign, it remains to be seen if this is a good thing or a bad thing. Either way, the skin on his thumb is the bigger issue, not when or how much he throws. The injury has prevented the 31-year-old from competing at his best.

Bosio said Arrieta will battle through it, but the thumb is affecting Arrieta's grip, which in turn changes how he delivers the ball.

“Not the normal flight on his pitches,” Bosio said. “It shows. He wants to power through it. It’s been an issue. He won’t make excuses.”

Bosio said the crazy weather during April and May didn’t help matters, either -- the skin issue made handling the ball in bad weather even more difficult -- but it’s not known if the changes in Arrieta's grip have been a factor in his well-documented velocity drop. His average fastball velocity was up a tick in his most recent start -- to 92.6 mph from 92.2 mph -- after not throwing on the side. It’s possible the speed could go up again after Arrieta only played catch all week. Bosio said the Cubs' training staff has been trying “new treatments” on the skin around Arrieta’s thumb, but until he takes the field on Saturday, no one will know how he’ll hold up. Still, Arrieta is like the rest of the staff: He wants the ball.

“They are freaking warriors,” Bosio said. “[They] want to pitch through every little ailment.”

All of which brought up the question about the disabled list: Could Arrieta have benefited from a stint on the DL? Could he still?

Bosio made it sound as if the Cubs' current position in the standings and, more important, the health and production of the rest of the staff are reasons to keep Arrieta off the DL. Kyle Hendricks already is on the shelf, John Lackey has been trending the wrong way, Eddie Butler still is trying to establish himself and Mike Montgomery is an 80- to 90-pitch pitcher right now. It has put a strain on the entire staff, with Maddon admitting Friday that the Cubs have already “used up” their starting-pitching depth.

“There comes a point where it’s not too bad to do it,” Bosio said of putting Arrieta on the disabled list. “It’s a fine, sketchy line. It’s a big question mark right there.

"If we could have done it, we would have."