PITTSBURGH -- The diagnosis is in.

Prior to Monday night's 8-2 loss to the Astros at PNC Park, the Pirates announced that they expect Oneil Cruz to return to action in four months after he underwent surgery on Sunday evening following his awkward collision with White Sox catcher Seby Zavala, a crash that injured Cruz and caused the benches to clear.

The surgery, performed at Allegheny General Hospital by Dr. Greg Altman and Dr. Darren Frank, stabilized Cruz’s left fractured fibula and addressed an injury to the syndesmosis, a fibrous joint held together by ligaments located near the ankle. Manager Derek Shelton expressed a bit of relief that the injury was limited to the ankle region and not other parts of the left leg.

Shelton said he visited Cruz at the hospital on Sunday night and FaceTimed him on Monday morning, noting that Cruz was in better spirits following the surgery. When asked about Cruz’s timetable, Shelton said he took more solace in the fact that Cruz was OK.

“The biggest thing for me today was when we FaceTimed him and he smiled,” Shelton said. “You guys have been around him; that smile is infectious. So, just to see that out of him a little bit, that’s where I’m more concerned. We’re talking about a 24-year-old kid here. … My concern is more about the kid than worrying about a timetable or what’s going on.”

With Cruz on the injured list for the next several months, Shelton said that Rodolfo Castro will get the majority of starts at shortstop. Castro has primarily played second base during his Major League career, but the 23-year-old is plenty familiar with shortstop, having logged 161 Major League innings and 426 Minor League innings at the position.

Shelton said his confidence in Castro is “high," referencing the tough play Castro made at shortstop in the eighth inning of Sunday’s win to prevent Tim Anderson from reaching base. Ji Hwan Bae, who has played 726 Minor League innings at shortstop, will see time at the position as well.

"Obviously, losing Oneil is a blow because he's a big part of what we do on both sides of the ball,” Shelton said on Sunday. “The flip side of that, because of the depth we've created over the last couple years we're probably in a better spot to handle it than we have been previously."

"Physically and mentally, I’m ready for any position they put me out there to play," Castro, who hit an RBI single and worked a walk in Monday's loss, said through team interpreter Stephen Morales on Monday. "I’m ready for anything the team needs me for."

For the Pirates, the loss of Cruz is their first true test of the season. They’ve started the season strong, winning six of their first nine and earning back-to-back series victories, a feat they accomplished just once last season. The vibes have been great so far, but Cruz’s injury has real potential to squash that momentum.

As Andrew McCutchen said on Sunday, there is no replacing Cruz, a one-of-one talent with an unparalleled combination of power, speed and arm strength. For now, all the Pirates can do is embrace a next-man-up mentality and attempt to match Cruz’s production in the aggregate.

“Nobody likes to see one of your friends get hurt and have to miss time,” said Bryan Reynolds, who was named the National League Player of the Week for his play last week. “I’ve been saying since the beginning that our identity is bouncing back from adverse stuff throughout the games. It’s just going to be another test for us, but I think we’ll respond well to it.”

“It gives someone else an opportunity to showcase what they can do, whoever that that may be,” McCutchen said on Sunday. “It gives them an opportunity to get more at-bats under their belt or whatever that it is. A prime example: Josh Harrison. He's a guy that was kind of an up-and-down guy, option guy. In 2014, he gets a chance because someone goes down and he becomes an All-Star and it's history from there.”

With Cruz on the 10-day injured list, the Pirates recalled utility man Mark Mathias from Triple-A Indianapolis. Mathias has primarily played second base, logging more than 2,000 Minor League innings there, but he has spent time around the diamond. Along with 406 professional innings at third base and 203 Minor League innings at shortstop, Mathias has played first base, left field and right field.

Along with his defensive versatility, Shelton praised Mathias’s offensive production over the last two seasons. In 2022, Mathias posted a .940 OPS in 58 Minor League games and an .825 OPS in 30 Major League games. In nine games with Triple-A Indianapolis this season, Mathias slashed .333/.459/.467 with a home run and a double.