Technically this is a clean play.
Matt Holliday of the St Louis Cardinals intentionally slid into the knees of San Francisco Giants 2nd baseman Marco Scutaro to break up the double play. The slide worked and Scutero missed the double play, but he was hurt pretty bad and eventually had to leave the game to go get his hip x-rayed.
Was this play dirty, you be the judge.
The Giants went on to win the Cardinals 7-1 to tie the NLCS one game apiece.