"I think what we'll do is put him on [the DL] and then just re-evaluate him as we go," Mozeliak said. "He's been put in a splint today, and once the swelling goes down, he'll be put in a cast. At some point, we'll re-evaluate. Obviously, we're hopeful that it will be shorter rather than longer."
Diaz sustained the fracture on Sunday when he took a 95-mph fastball from Marlins right-hander Andrew Cashner off his hand. He had trouble flexing his thumb immediately afterward and was removed from the game. Following the game, however, the Cardinals were optimistic that his absence would be short. The initial set of X-rays taken at Marlins Park had not shown a fracture. That changed with a visit to a hand specialist.
Diaz, an All-Star last month, was putting together a sensational rookie season, hitting .312/.376/.518 with 57 RBIs and 64 runs scored.
Though the Cardinals will be hard-pressed to replace Diaz's production as the team's two-hole hitter, they do have an easy fill for the shortstop position. The Cards were already anticipating activating Jhonny Peralta from the DL on Tuesday. Now when they do so, it'll be to make him the team's everyday shortstop.
The Cardinals did not, Mozeliak said, pivot in the final hours before the non-waiver Trade Deadline to pursue another infielder.
"You're not going to go out and find that type of impact player," Mozeliak said. "And the fact that we have Jhonny Peralta activated tomorrow, I think he can just slide right in there."
Brandon Moss is also slated to be activated from the DL on Tuesday, with Matt Carpenter to follow three days later. Carpenter will be getting work at both second and third base on his rehab assignment this week so that he is ready to play either position. The versatility of Jedd Gyorko, Greg Garcia and Kolten Wong will allow the Cardinals to mix and match across the infield until Diaz returns.
"Obviously, we were very disappointed to learn of Diaz's injury, but when you think of where this club was going to be tomorrow with getting two of our everyday players back healthy and then obviously getting Carpenter back at the end of the week, there was a high level of optimism," Mozeliak said. "We still have that, but certainly, losing Diaz did not help that."
Jenifer Langosch has covered the Cardinals for MLB.com since 2012, and previously covered the Pirates from 2007-11. Read her blog, follow her on Twitter, like her Facebook page and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.