Bruce believes United's back four will be crucial on the run-in.
He told the Mirror: "Of course they have missed Vidic, but Jonny Evans has now played over 20 league games and has very quietly done extremely well.
"He's only 23, he's played in big games and has handled himself brilliantly.
"It's also important that Rio Ferdinand has come back and just given them that stability. I think defenders get better with age. Even though you might lose that half-yard of pace, it gets easier.
"The art of defending lies in your concentration levels, and that is something which gets easier with age.
"It's particularly important at United, where you are constantly on the attack and you need to stay switched on even when you might not have too much to do."