Not sure whats so surprising about that, he neither plays as a striker, nor has really played much since then due to injury, during his last uninterupted spell in the team he was the leagues top scorer, since January or so he's been on and off injured with fairly few games being played.
Either way, I still can't believe Petrov starts, he's almost as useless as SWP but both get a couple flukey goals now and then. He's been down the right wing maybe, 5-6 times already and every single time stops and comes in on his left, theres few players in the entire league so completely one footed that they won't even consider a cross on the other foot. Considering Bellamy has played very well on the right and is right footed, and Robinho plays well on the right the insistance on playing Petrov on the right seems a tad strange.
Defenders who can't read what he's going to do should be embarassed.
You don't find it surprising? Hmm.
And cutting left footers in from the right is very effective, they wouldn't play him there if they didn't expect him to cut in. They are probably wanting him to cut in near the box, and have a shot.