Former undisputed world heavyweight champion and Hammers fan Lewis gave a rousing pre-match team talk at Upton Park on Tuesday night.
Diame said: "It was great. He is a great boxer and he told us to go out and fight like he has all of his life so that was good for us.
"We started very badly this season but now we are starting to be focused on what we are doing, there are a lot of players back now.
"Everyone wants to be in the starting XI and that is why we are having this good moment - I hope it stays like this until the end."