Nothing is certain but the chances are that he would have done much better than CMS, you make it sound like it was a bit hit and miss ignoring the fact that most of the other players who came up from League One side acquitted themselves well in the Championship and he was one of our class...
He looked quality for us in League One, took a season to shine at Palace, got a bad injury and took a while to make his mark in the Premier League. I have no idea why you would question whether he could have performed for us at this level, weird.