However, while manager Sam Allardyce will be keen not to over-expose him so soon after his return, Duff is desperate to get as much football under his belt as possible.
"It's been busy, but that doesn't bother me because I'm just delighted to be playing again," he said.
"The results have been disappointing though, especially Chelsea (a 2-1 defeat) when we felt we could have got the win and definitely the draw.
"But I'm feeling great in myself and would say I'm just about 100% fit now.
"I came off with a couple of minutes to go against Chelsea but I felt like I could have run all day."