PITTSBURGH -- The Pirates on Sunday activated catcher Elias Díaz and put catcher Jacob Stallings on the 10-day injured list with a cervical neck strain.

Diaz was set back in Spring Training by a bacterial virus that caused him to miss two weeks of workouts. The Pirates had to put their backup catcher on a modified Spring Training program, which concluded with a rehab assignment in Triple-A Indianapolis. Diaz was not in the Pirates’ lineup against the Giants at PNC Park, but he was all smiles in the clubhouse on Sunday morning.

“I’m so happy to be on the team again,” Diaz said. “I’m really excited to be here and be part of the team again.”

Diaz, 28, enjoyed a breakout season last year as he and Francisco Cervelli formed the Majors’ most productive catching tandem. He hit .286/.339/.452 with 10 homers in 82 games and ranked sixth on the team among offensive players with 1.8 Wins Above Replacement by FanGraphs' measurement, which includes catcher framing.

“Diaz’s value behind the plate is real. He’s grown as a catcher, game-caller, receiver and thrower, and the bat has been very productive at times, especially against left-handed pitching,” manager Clint Hurdle said. “He’s going to make us better.”

Stallings’ stint on the injured list was made retroactive to Thursday. He last played on April 12; the Pirates have been leaning on Cervelli behind the plate so far this season. Stallings is out of Minor League options, so his injury gives Pittsburgh more time to make a decision regarding whether he will be designated for assignment and potentially lost on waivers.

The Pirates could receive additional reinforcements in the coming days, as Hurdle said right fielder Gregory Polanco might be ready to return during Pittsburgh’s upcoming four-game series against the D-backs at PNC Park. General manager Neal Huntington cautioned that Polanco’s arm strength won’t be the same as it was before his September shoulder surgery, but they believe he’s nearly ready to help the team.

“We feel really good about where he is and just can’t say enough about how much work this young man’s put in and how his body’s responded because of how he’s taking care of himself,” Huntington said. “We anticipate that, over time, Gregory will get velocity back. We may even have a better-throwing right fielder at some point in time because he understands the value of getting to the ball, getting it underway accurately and quickly, and now we get some velocity back, too.”

Colin Moran, second baseman?

Colin Moran made his first Major League start in left field earlier this season, and he added first base to his repertoire during Spring Training. He got another new look on Sunday afternoon, making his first professional appearance at second base behind right-hander Chris Archer.

Moran last played second base as a freshman in high school, but the natural third baseman occasionally moved to the right side of the bag when the Astros shifted their infield.

Slotting Moran at second seems like a bold move by the Pirates in an effort to get his bat in the lineup while Adam Frazier is out with back spasms, but it’s not unprecedented by any means. The Brewers moved third baseman Travis Shaw to second after acquiring Mike Moustakas last season, and they were mostly successful with what Hurdle called their “goal-line defense” due to aggressive infield shifting. It also makes more sense to put an inexperienced infielder behind Archer, a strikeout pitcher with a 42.1 percent ground-ball rate this season.

“I think we are more creative and we think more outside the box than ever before. There’s things we’re trying now that we wouldn’t have tried back then because it was tradition,” Hurdle said. “There were generations that held onto tradition for a lot of the right reasons. I think we’ve also found out over time that tradition can be a vision-killer.”

Injury updates

• Shortstop Kevin Newman (lacerated finger) should begin a rehab assignment this week, Huntington said. With Cole Tucker up to play shortstop, Newman will get some work in the outfield along with shortstop and second base.

• Left fielder Corey Dickerson (strained shoulder) is playing catch, but he is not yet ready to begin a rehab assignment.

• Frazier (back) was not in the starting lineup for the third straight day. He ran sprints on the field before Sunday’s game.

• Huntington said it was still too early to provide a timeframe for the return of Starling Marte and Erik Gonzalez, who were placed on the injured list on Saturday following their collision in center field on Friday night. Gonzalez figures to miss more time due to the nature of his injury, a tough turn for an infielder finally getting his first chance to play every day.

“He’s really down, man. He knew he had the opportunity,” Huntington said. “At the same time, we’ve reaffirmed with him that we still like him and believe in him and we’re going to need him at some point this year.”

UMPS CARE auction underway

Major League umpires are offering more than 400 items -- including autographed memorabilia, VIP experiences and ticket packages -- during the 11th annual UMPS Care Charities Online Auction. The auction is live until 10 p.m. ET on April 29.