I think Rosenberg has had a part time gig at SI, possibly even before the little expose he did. I highly doubt that that piece is what got a national publication to suddenly notice him. When you are a columnist at a major metro publication for 10 years or more, you're gonna get noticed.
Also worth noting, Rosenberg never mentioned that piece in his farewell column. He's quite aware that probably 15% of the Free Press readership associates him with that piece and only with that piece. I don't think he's necessarily proud of it to the point that he wants to tout it, but I don't think he feels he did anything wrong either. It's just another clipping in his past.