I bet Mike Portnoy used only 1/3 of his usual drum kits and 20% of his talent and skill when he recorded drum part in Avenged Sevenfold - Nightmare album. He stated in an interview :-

"Well, I had to show a lot of respect and restrain but that's OK; I was OK with that. To me this was a very fragile situation and a sensitive situation for the bandmembers who had never played with another drummer and were just fresh in the mourning period. So I had to be very, very respectful of the sensitive nature of this session and I wanted to respect The Rev and pay tribute to him. So, yeah, I wouldn't say it was hard; I had to kind of shift gears from what I normally do. Normally I go in there and do things myself in my own way and I self-produce my drums but in this case I had to kind of just wear a different hat. And because of the circumstances it made it kind of easy to swallow."

His basically point that he was holding back when he recorded his part due to respect to the band.