Collins said: "There's competition all over the park. We have a few injuries, but we're developing a big squad and that's what you need in the top flight. You look at Liverpool and they had John Arne Riise on the bench at our place - a quality left-back.
"Hartey coming in is a challenge and I'm ready for that. It makes you up your game on the training pitch and you certainly have to up your game on a Saturday."