Advice please? Doesn't mean I'm going to take it, just want some opinions!?

So I have this friend, let's call her Stacy. She has this friend, let's say Jordan. Jordan and Stacy are always switching boyfriends, liking the same guy, and taking guys from eachother. Okay thought I would get that through. Now here's the problem. Stacy and I like the same guy. She liked him first, so I said I would back off and let them get to know each other. (Jordan hooked them up, and neither Stacy nor Jordan has met him in person, I have though.) Well turns out that this guy likes me. He doesn't like Stacy at all. He thinks she self-centered, and all that fun stuff. I don't want to be like Jordan and take Stacy's guy that she likes. I just don't kno what to do! Ant ideas? And I'm probably not going to tkae any of this advice, I just want to see what other people would do!