PITTSBURGH -- The Pittsburgh Pirates remain in contention for a playoff spot, but not without continued uncertainty regarding their rotation.

Right-hander Gerrit Cole (5-6, 2.99 ERA) will try to get back to .500, far below what the Pirates expected from him, on Wednesday when Pittsburgh closes out a two-game series with the Seattle Mariners.

After a day off, the Pirates' scheduled starter for Friday at Milwaukee is TBD -- a fellow who has gotten quite a bit of face time on the Pittsburgh schedule of upcoming starters.

The Pirates are dealing with a shoulder injury to promising young starter Tyler Glasnow and less-than-stellar results from Cole and Francisco Liriano, the latter two expected to anchor the rotation. The team is being cautious with another rookie, Jameson Taillon, although it looks as if he might be sticking in the rotation.

Jonathan Niese, Juan Nicasio and now Jeff Locke have pitched their way into the bullpen, although Locke -- who made his first relief appearance Tuesday, allowing a hit but no runs in two innings -- for now is expected to miss just one start.

Liriano looked to be breaking out of a funk when he struck out 13 batters Thursday in a 5-3 win over the Brewers. On Tuesday, though, he reverted to early-season form, struggling with his control and allowing seven runs on eight hits in 3 1/3 innings in a 7-4 loss to Seattle.

So it is Cole's turn to try to give the Pirates another in a series of what have seemed to be turnaround performances, although many of the previous ones have not stuck.

On Saturday, Cole took the loss as Pittsburgh fell 4-0 to the Philadelphia Phillies, but he was encouraged about his outing, his second since coming off of the disabled list. He missed a month due to a right triceps strain.

"It was a good step in the right direction," he said after giving up one run on six hits over six innings. He struck out seven and walked one.

"I thought there were a lot of pitches that were thrown really well that they couldn't pick up. It's good to see stuff like that. Hopefully, we can build on it."

Cole's opponent Wednesday will be James Paxton (3-4, 4.18 ERA). The Seattle left-hander will start against Pittsburgh for the first time in his career.

Paxton ended a run of three starts without a win Saturday when he pitched seven innings in a 2-1 victory at Toronto. He allowed the lone Blue Jays run on three hits. His nine strikeouts were one shy of his season best.

"I know he and (pitching coach Mel Stottlemyre Jr.) have been working on a couple of things, and it certainly was evident with his ability to spin it," manager Scott Servais said of Paxton. "That was the best curveball he's had all year."

It was an adjustment Paxton took to happily.

"I was creeping down a little bit and getting too sidearm, getting on the side of the ball," he said. "It wasn't allowing me to get on top of the curveball. Bringing my arm up a little bit more has allowed me to get on top of that curveball."

The relief crew behind Paxton on Wednesday might include the newest member of the Seattle pitching staff.

After Tuesday's game, the Mariners announced they acquired reliever Drew Storen and cash considerations from Toronto for pitcher Joaquin Benoit. Storen, 28, is 1-3 with a 6.21 ERA with 32 strikeouts in 38 relief appearances with the Blue Jays, who designated him for assignment Sunday.

In his first six major league seasons, all with Washington, he was 21-13 with 95 saves and a 3.02 ERA.

"Obviously, this has not been Drew's best season, but he is closely linked to a run of great success pitching in the back end of very good bullpens," Mariners general manager Jerry Dipoto said in a statement. "Hopefully, this serves as a change of scenery and over the next two months we can get him back on track."