Cardinals shortstop Jhonny Peralta has what appears to be a torn ligament in his hand, and he could miss two to three months. The loss is significant for the Pirates' rivals, who don't have any other shortstops nearly as good as Peralta. They could go with Morgantown's Jedd Gyorko at the position for awhile, or perhaps someone like Greg Garcia or Aledmys Diaz. As MLBTR's Jeff Todd notes in the piece linked above, the Cards could simply have signed Ian Desmond had Peralta's injury happened a bit earlier, but Desmond recently came to terms with the Rangers. At this point, there isn't much on the free agent market, so if the Cardinals want to acquire another shortstop, it will likely have to be through a trade.
Of course, the Cardinals' 2015 team suffered any number of injuries, but none that ever stopped them. The organization always seems to find ways to plug in ordinary-looking players like Gyorko or Garcia and keep on ticking. Common sense suggests, though, that the Cardinals will miss Peralta, who provides excellent offense for his position -- he's hit a total of 38 homers in his two years with the team.