At a time when the Arizona Diamondbacks' rotation is in flux, left-hander Patrick Corbin could do well to give them a good start Friday against the Pittsburgh Pirates at PNC Park.

Arizona expects several injured starters to return soon, and roster decisions are coming. Corbin's spot would not seem to be in jeopardy, but he is coming off some inconsistent performances.

In early May, he was 4-0 with a 2.12 ERA. He goes into Friday's start with a 6-3 record and a 3.48 ERA and is expected to be matched against Pittsburgh's Ivan Nova (4-5, 4.42).

Corbin has given up at least five runs in three of his past four starts, including five against the Pirates at home on June 11.

In his most recent outing, a 5-1 loss to the New York Mets on Saturday, he gave up all five runs on eight hits in six innings.

"Just a couple mistakes there," Corbin said of the game against the Mets. "If I locate better, different outcome."

Corbin, who is 1-2 with a 5.90 ERA in five career starts against Pittsburgh, hasn't been completely off lately. He has 19 strikeouts in his past 16 2/3 innings.

But against the Mets he could not pinpoint his curveball or his fastball.

"I just thought the pitch sequencing was a little bit off, and I thought there were a lot of fastball mistakes out over the plate that were hit, and they were handled by the Mets," Arizona manager Torey Lovullo said. "Didn't really get to the secondary stuff the way he typically does, and I think it's more a product of the game plan and sequencing."

Lovullo hasn't lost confidence in Corbin.

"Worrisome? No. Not an issue for me whatsoever. We know that the season is going to have good and bad moments," he said.

The Diamondbacks (41-33) cruised to a 9-3 win in the series opener Thursday as the Pirates (36-38) lost for the third time in four games.

Pittsburgh dropped two of three last week at Arizona.

Nova was initially scheduled to start Thursday, but the Pirates opted to move everyone back a day when Wednesday's game against Milwaukee was rained out, rather than do any shuffling with his rotation.

"This group right here has shown the ability to be flexible, to be resilient and also shown some benefits from an extra day (of rest) every now and then," Pirates manager Clint Hurdle said.

It didn't pan out that way. Chad Kuhl, who started the opener against Arizona after warming up several times Wednesday when there was false hope that the game against Milwaukee would be played, got rocked by the Diamondbacks for eight runs in two-plus innings.

Nova is coming off two good starts, going 2-0 with a 1.54 ERA since he was removed from the disabled list (sprained finger).

On Saturday, he struggled with his curveball, but it didn't stop him from allowing just one run and five hits in six innings of a 6-2 win over Cincinnati.

"Even though I walked a couple guys, the fastball command is better than what it was before I hit the DL," Nova said. "I think I've been able to control it a bit better. I think that's been the key."

Nova is 1-1 with a 4.00 ERA in three career starts against the Diamondbacks.