PITTSBURGH -- Gregory Polanco couldn't get the awkward slide into second base last September that dislocated his left shoulder out of his head. The Pittsburgh Pirates right fielder pored over the video during his lengthy rehab to the point where it simply got to be too much.

"It was terrible," Polanco said. "I watch it a lot of times and it was not a good feeling to watch it, so I stopped."

He focused on the long road back, one that reached a significant milestone on Monday when the Pirates activated the 27-year-old off the injured list and put him in the lineup in time for the opener of a four-game series with Arizona.

Polanco was legging out a double against the Miami Marlins on Sept. 7 when he tried an unorthodox slide to avoid a tag. He appeared to leap in the air before extending his left leg toward the bag, tumbling forward and starting a sequence that ended with his left shoulder dislocated and the labrum in his throwing shoulder torn. He had surgery on Sept. 12, ending a season in which he hit a career-high 23 home runs.

Pittsburgh estimated Polanco could be out up to nine months. He made it back in a little over seven, a testament to the way he pushed himself even while spending time back home over the winter in his native Dominican Republic.

"They ask me to do extra, I do extra," Polanco said Monday. "My homework too. Back home they would ask me to do exercises, and I did it."

Polanco joins a club off to a 12-7 start despite having a lengthy injury list that includes outfielders Starling Marte, Corey Dickerson and Lonnie Chisenhall. Polanco hit .300 with five RBIs and two stolen bases during a rehab assignment with Triple-A Indianapolis. He has also worked extensively on his sliding, a portion of his game that he struggled with before getting hurt.

"Unfortunately the collateral damage that he incurred from a poor sliding technique, I think that got his attention," Pirates manager Clint Hurdle said. "And sometimes pain can bring specific attention to an immediate area, and I think in this case it was sliding. He worked very hard to tighten that up and get that in a better place."

Polanco will be prohibited from sliding headfirst and he still isn't near 100 percent arm strength, though Hurdle noted Polanco's velocity is up significantly from the end of spring training. Pittsburgh will try to help Polanco by pushing cutoff men farther into the outfield.

Though Polanco pledged to stay aggressive both on the field and on the bases, he will also do what he can to avoid another mishap like the one that led to the first significant injury of his career.

"When you make mistakes like that, it costs you," he said. "It cost me a lot of games for me and you know, maybe my arm wouldn't be the same this year. I'm here. I'm happy that I'm back here and I'm able to join the team and enjoy it with my guys."

To make room for Polanco, the Pirates optioned left-handed reliever Steven Brault to Triple-A.