PITTSBURGH -- Rookie Dario Agrazal started on Sunday afternoon at PNC Park, taking right-hander Chris Archer’s spot in the Pirates’ rotation. Five days after Archer walked off the mound with a shoulder injury, it’s still unclear how long Agrazal will be filling in for the veteran starter.

After being placed on the 10-day injured list on Wednesday, Archer received a second opinion that confirmed he has inflammation in his throwing shoulder, general manager Neal Huntington said on Sunday. The Pirates will reassess his status in a week to 10 days then determine what comes next.

On his weekly radio show with broadcaster Greg Brown, Huntington said the Pirates don’t want to make Archer feel like he has to rush back to earn a spot in the rotation moving forward. Huntington admitted that Archer’s results haven’t been as good as the club expected, but also expressed confidence in Archer’s performance, saying on KDKA-FM that the club has seen “really positive signs” that he’ll be a “really good” starter in the future.

Archer, who will turn 31 next month, has made 33 starts in a Pirates uniform. In roughly a full season’s worth of work, he owns a 4.92 ERA with 203 strikeouts and 33 homers allowed in 172 innings. After altering his pitch usage, he took some steps forward coming out of the All-Star break. In his last eight starts, Archer struck out 55 and walked 14 while giving up 39 hits in 41 innings; during that stretch, he held opponents to a .244/.309/.394 slash line, but the Pirates won only one of those games.

This is the final guaranteed year of Archer’s contract. The deal includes a $9 million club option for next season, and it seems likely that the Pirates will exercise that option rather than creating another hole in their rotation. Asked if Archer’s injury will affect the club’s decision on whether to pick up his option, Huntington replied simply, “No.”

Until Archer returns, Agrazal will get a chance to prove himself heading into next season. Huntington said Agrazal “is going to do everything in his power to earn a rotation spot going forward.”

“He’s got an opportunity to go out and take some quality innings and continue to show the guy who was really good for those three or four starts and show that he can make an adjustment back to the league, as they made an adjustment on him in his last three starts,” Huntington said. “He’s fun to watch. He’s a pitcher. And he moves the ball around. He doesn’t try to overpower people, yet you can get a 93 mph fastball by a good hitter up in the zone if you set it up well.”

Agrazal allowed four runs on seven hits while striking out five over five innings during the Pirates’ 9-8 win over the Reds. After picking up his third win, the rookie said he hopes to improve -- and prove himself -- if he’s able to start on a regular basis down the stretch.

“Being able to be in that rotation and gaining more experience, more opportunities, more reps, I definitely feel I’m going to be able to grow from that,” Agrazal said through interpreter Mike Gonzalez. “Hopefully it’ll continue going forward.”

Callup questions

Next week, Major League rosters will expand from 25 to 40 players. Huntington said the Pirates will make their callups based on “opportunity, [if they're] ready and how do they fit in the bigger picture?”

For the final month last year, the Bucs brought up a handful of younger players who had a chance to make the team on Opening Day. This September should be similar with prospects like Cole Tucker set to return.

“We’ll bring up some guys who are going to compete and show us what they can do,” Huntington said. “Pablo Reyes was a great September story last year. We’ll add some position players, some pitchers and still look to compete and win games.”

Will one of those callups be third baseman Ke’Bryan Hayes? Huntington has been reluctant to say the Pirates will bring up Hayes, the club’s top position-player prospect, in part because of the offensive struggles he’s had this season. Hayes is making it interesting, though.

The 22-year-old third baseman entered Sunday batting .315/.354/.449 in August, and he recorded multiple hits in each of his last four games. Might that change management’s mind?

“It could, in theory. We love the defense. We love the young man,” Huntington said. “We want to make sure we understand what this good stretch means, how he’s turned the corner, and how does it play at the Major League level, and do we feel he’d be ready to go on Opening Day next year? And if so, what does that mean for the bigger picture?”