You're missing my point here Curr....we don't know he can't defend because he has never really been put in a position where he had too. He did fine on the left side of midfield where he had to track back, all he needs to do is get stuck in and that is all Camo ever really does anyway. It is not like Camo is an excellent man-marker. His job is to get the ball anywhere in midfield and make something happen as is Gio's job. Just like Camo has Melo/Sissoko/Marchisio for cover, Gio would be given the same perks and freedom to run with speed. Gio, IMO, is quicker than Camo is nowadays.
You can't compare Trez defending to Gio defending at all. Trez is a striker, Gio is a midfielder and should be played in their positions. Otherwise, what the heck is the point of keeping Gio? Just "incase" Diego gets hurt or at 24 years old gets tired? I don't see why we couldn't just try him there. Some people here are so confident that an clumsy only left footed De Ceglie should play in our midfield. If people would want to put DC in a 3 man midfield with absolutely hardly any use of his right foot, clumsy with the ball at his feet, and shaky defending then I don't see why it would be a problem to try a near ambidextrous, quick, creative little genius like Gio in a 3 man midfield instead of letting him sit on the bench all the time.
You put two strong, complete DMs like Sissoko/Melo and an almost Marchisio next to Gio just like we do with Camo I am confident Gio will produce the same results.
Camo doesn't really defend, he gets pissed and commits silly fouls anyways. Whenever he loses the ball, honestly how many times have you seen Camo bust his ass back to get it back? Not often because he just stops and waits for our D to get it back.
:edit: Another point here...in a 3 man midfield our 3 mids need to be extremely mobile, ESPECIALLY the creative one because they are the spark needed to ignite the attack. DC is not mobile for one, he is limited because of his inability to use his right foot effectively, so to I suppose strengthen my "argument"...the fact that Gio is so willing to use either foot necessary and ABLE to do so makes him quite capable to do the job in a 3 man midfield. He can do the Camo role nicely where he would make himself available to get the ball. Look how well he turns with the ball at his feet (Chelsea game last year in CL to site an example).