No he did not, Hustini. Other than against Inter when he was sacrificed to completely blunt Maicon, he almost always bunched up in the middle to make a midfield trio. Its not an opinion, its where he played. I saw it with my own eyes...regardless of the 'official formation' showing him as a left midfield in a midfield 4. Krasic was NEVER a RM, althoug he was always shown as such on a formation sheet or screen. the formation was much more a 4-3-3 or a 4-3-1-2, with that 1 been Krasic wide right, somewhere between a right winger and a right wing forward.
Grosso was shocking, but in the brief flashes when he was useful, it was when he was attacking. whereas on the opposite flank, sorensen hardly attacked at all, and krasic did not like to track back, so Melo had more work to do there. A weak but true point.
You could say that the trio of midfielders would work far better with a stronger, more intelligently moving offence, and a much more balanced defence. That would make sense...maybe in that situation, Marchisio would be brilliant in a 3, but last season, when we often looked like we had 3 in midfield, he was generally poor, not making mistakes as such, but consistently failing to impose himself on an area of the pitch where its essential to impose yourself. Its easy to see that he used to play as a tre quartista, as he is very easily outmuscled when playing as a CM/DM...that also explains why he scores more than Melo; offensively he is a much better player.