Okay so my friend's been sleeping with this guy lately who doesn't really do relationships much, is more of a one night stand kind of guy. Anyway they've been sleeping together for a few months and I know she's holding back from saying it, but I think she's starting to develop feelings for him and I guess she's holding back cause of his reputation

Every time I bring it up she says he's not the type to get feelings etc etc. Anyway whenever we're out and he's around I swear every time I look at him he's looking at her, and I swear there's a look of affection. There's always a slight smile when he sees her and he never seems to peel his eyes off her (even if she never sees it). Anyway, do you think its possible he might like her or do you think its impossible?

Depends on their ages.
No one will stay a player all his life. Anyway what is a player?
The best thing to do, is for both of them to talk about it. Otherwise it can get messy!

There is no way to tell if its love, lust, or attraction.Time will tell though.