Foster is currently plying his trade in the Championship with Watford but has opened up on his days in the Premier League, naming his least favourite opponent ever, the biggest hardman and the worst trainer he's come across.
Asked who he disliked playing against the most, Foster named an ex-Chelsea striker whose reputation for being an awkward opponent precedes him.
"He would just snarl and scratch and he wouldn't leave you alone and he wouldn't give you a second's breathe.
"And do you know what, Luis Suarez was a bit like that as well. He was horrible to play against, he would kick you, he would scratch, he would do anything.
"But just pure winners, I love those type of players. You want those types of players on your team. Animals!"
Another type of player Foster believes is fundamental to achieve success is a tough-tackling, no-nonsense figure.
Having been in the same dressing room with many throughout his career, who was the hardest?
"[I was with Roy Keane] only for a little bit and he did scare the life out of me, to be fair. He was a scary bloke,' Foster added.
"Nemanja Vidic was a bit of a sicko as well, to be fair. I'd say Nemanja. He would happily put his head on the end of someone's boot to stop a ball going in. Yeah, sicko."