From the guys over at MMARated.com:
MMARated.com has learned from several very reliable sources that Ken Shamrock sustained a cut above his eye in the last 24 hours while training and WILL NOT be fighting in tonight's main event bout against Kimbo Slice.
EliteXC officials are scrambling to find a last minute replacement for Shamrock. Amazingly, we have heard that Shamrock's brother, Frank, who is calling the event for CBS, offered to step in at the last minute but is ultimately not fighting. EliteXC has offered Slice a last-minute replacement in the form of Seth Petruzelli. Petruzelli was scheduled to fight Aaron Rosa tonight.
As of right now, Kimbo has yet to officially accept the fight.