So Diego didn't fare so well. What about Koschek?
He is a better wrestler than Diego and a better striker. He doesn't take a very good punch (see Paulo Tiago) , which would bode well for BJ... The lightweight division is highly competitive, but not at BJ's level. Outside of GSP and other huge welterweights (see Jon Fitch), I think Kos stands a decent chance against the LW Champ.