I think it was frustration over Riley, but it could have been a myriad of things..
(1) Rio was upset that it was a foul?
(2) That Riley ended the match while the ball was in play or while Drogba was recieving treatment?
(3) Rio thought a foul was called when it was actually just the end of the game?
Who knows, really...
I was more concerned about Berbatov's work ethic. With Park, Hargreaves, Fletcher and Rooney working their asses off all around him, he sure seemed to be standing around a lot. I would never question SAF, but bringing Ronalado in with a goal lead seemed an odd choice. I'm sure Tevez was an eventual sub, but Van Der Saar ruined that.