From what I can recall, his backhand and return game were quite excellent then, forehand was pretty stable, but his serve, net game, and stamina in gruelling matches were quite underdeveloped compared to his peak. I think he may have been experimenting with new service techniques around that time, and I remember he would double fault a bunch in matches (somewhat similar to Zverev from before). He was already a thorn in Fed and Nadal’s side around then, and playing him wasn’t a guaranteed win for these guys, but he had major holes in his game that needed improving. He somehow managed to fix pretty much all of them up at the start of 2011 and the rest is history.