athlete

If you're on a school team, your coach probably won't let you rush.
But if they do, you'll be treated like anybody else. You'll need recs, like everybody else.
Yes, it would be great to pledge an athlete, but that person is usually not going to be able to come to a lot of stuff, especially during their playing season. Practice is almost as intensive as playing, so she'll be paying a lot for something she can't participate in very much, plus the sisters will miss their time bonding with her.

I would definitely say that sororities look for girls that are involved--especially girls that are cheerleaders, crimsonettes, or on Crimson Cabaret. Houses normally fight for girls like that.

As for other sports, very few athletes choose to rush because they are already making friends on their team and they don't have very much time. Being in a sorority is a huge time commitment and so is being an athlete, which will always come first to being in a sorority. As much as I love my sorority, it would not be worth paying $4000 a semester to not be able to do anything.