Doug Free is an unknown at this point. When he was a RT he was very solid and played at a pro bowl level, if you look up his stats for all year he was one of the better offensive lineman period. D posted that link before, I'll post it if I can find it.
Columbo also is much better then average. Dude has always been a beast of a RT, he was rushed back from injury last year which led to him being demolished vs Minny but he should have never been playing to begin with. He's still been an anchor on our line and has never been just average.
Kosier sucks IMO, people will point out how he was one of our best lineman last year and he did get better, but he's always sucked to me. Free is just an unknown, someone could just as easily say he's great as they could mediocre, hard to say for sure which one it'll be but there is alot more evidence to suggest he's better then mediocre.
Just because there is new blood on the line doesn't mean the entire unit will be worse. Do you really think Jerry would cut Flozell if he felt Free would be a downgrade? That's not even his style, and at worst it'll be a wash.