He beat Delpo at AO in the latter's last match before leaving the tour for a year for surgery. It's a very tough matchup for Marin for many reasons. Of course he has his chances, he can reach a very high level with his game and beat almost anyone; but if he is to face Delpo, let it be further in the tournament, not in round 4. Tsonga, Berdych and Tipsy are far more beatable opponents for him so Marin will be hoping to draw one of them I'm sure.
How unlucky he is he will get Delpo. I think he would beat all others.
However, Marin can beat everybody, but he can't beat mind. That's I am talking about all the time. If his head is "normal" (tennis wise) he would win a Slam instead Delpo 2009.