"You're going to lose players in the course of a season," Pirates manager Clint Hurdle said. "He's down. He's going to miss some time. We love him. We will miss him."
Harrison said Monday that he has not received an official diagnosis from the team's training staff, and he does not know how long the injury will keep him off the field. The injury could sideline him as long as six weeks, but Harrison will get a better idea of the severity after receiving a second opinion later this week.
"I'm still trying to figure out myself. It's pretty fresh," Harrison said. "Got to go through a few more tests with the training staff, see what I can do and what I can't, and we'll go from there."
With Harrison out, the Pirates will likely lean on infielder Jung Ho Kang as their primary third baseman, while using right fielder Gregory Polanco in the leadoff spot.
Harrison was his typically upbeat self when discussing his injury, joking that he'd play Monday night if it were up to him -- even as his swollen and heavily taped left hand hung by his side.
"It's always tough to sit out. But we've got a good team," Harrison said. "Clint has said it before: It's going to take us all."
The Pirates added Travis Ishikawa, claimed on waivers Sunday, to their active roster to fill Harrison's spot. Ishikawa can play first base and either corner-outfield spot, or serve as a left-handed bat off the Bucs' bench.
Pittsburgh claimed Ishikawa, who broke camp with the club last year, off waivers from San Francisco on Sunday, before Harrison's injury took place. The 31-year-old veteran was pleased to be back in the home clubhouse at PNC Park.
"It's good to be back, for sure," Ishikawa said. "These guys have already made me feel like I never left."
By using Ishikawa at first base on occasion, or late in games to replace Pedro Alvarez, the Pirates can free up versatile utility man Sean Rodriguez to help alleviate the difficulty of losing Harrison.
That flexibility will be a necessity this week, as left fielder Starling Marte is still considered day to day with discomfort in his left side.
Marte was out of the lineup Monday and expected he'd be sidelined a few days, though he has not heard anything about joining Harrison on the disabled list.
"I have to take a rest," Marte said. "I don't want to put more pressure on this and take a lot more time. I'll take a couple days off and get ready very soon."
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.