Casilla appeared to injure his knee covering first base on a Ben Revere groundout, as the pitcher left the game following the play. Giants manager Bruce Bochy revealed after the game that the injury had been bothering Casilla before the game starting, and that the reliever may have downplayed the extent of his injury to the team.
The right-hander did pitch effectively despite coming into the appearance banged up, as he did record outs to both batters he faced. Casilla will undergo an MRI later on Wednesday or Thursday to determine the seriousness of the injury.
Casilla is an important reliever for San Francisco, as he is tied for the most appearances out of the Giants bullpen this season with closer Sergio Romo. Casilla has a 2.20 ERA in 16.1 innings this season, and posted a 2.84 ERA in 63.1 innings last season. The relief pitcher does not strike a ton of batters out, especially for a relief pitcher, but is able to force a lot of groundballs.
San Francisco does own a deep bullpen, which could help offset any long-term loss of Casilla. Giants' relievers 2.68 ERA is the second lowest ERA in baseball behind the Cleveland Indians.