I think I like the same guy my friend likes?

A good loyal friend would undeniably back off. It'd be a betrayal if you went after him conscious of your friends feelings for him. If you went after him not only would you be demonstrating your lack of devotion to being a true friend, your lack of awareness to people's emotions, and lack of morality, but you'd also be hurting both your friend and yourself, because if you truly cared for your friend and this guy, you'd withdraw for their benefit, for their happiness. If you didn't do this, you'd only be displaying shallowness. It's better to be a river than to be a puddle, after all, right? But if the feeling between you and this guy is mutual, I don't necessarily encourage you to back off, but I do recommend you getting you getting your friend's blessings first.