Ben Johnson was a sprinter, you don't hear of marathon runners taking roids. Karl Malone bulked up as he aged. He didn't do it in one summer. I think you'd notice something funny about a guy who put on a ton of weight in a few months. First of all, the would have to do it in the off-season, as basketball isn't a sendentary sport like baseball, or a short season like football. I doubt any NBA player could take steroids and have a long career, or even one beyond a few years.
that's funny because i remember before the draft, people were saying the thing that would keep Howard from having an instant impact like Amare Stoudemire or Lebron James was that he didn't have an NBA ready body. A couple of months later, he shows up on opening day looking like David Robinson and noone even said anything.
Anybody remember Jordan when he's just came out of college, he's skinny, but later on in his career, he's thick with upperbody muscle. Lebron was like this when he's even in high school.
People do tend to gain weight as they age.... But Jordon did go off and try to play baseball for a year and change, wouldn't be surprised if he touched the stuff then...but from what I remember his issues were bat speed, not strength.
I used creatine years ago and as long as you drink a lot od water, the stuff works. Of course when you off the stuff, the mass will dissipate.