If the fight against Luffy was so intense that it brought back that much ailments, then that in of itself is a testament that he's not near Luffy's good side.He had ailments and the fight against Luffy made them come back, weakening him before his fight with Lao G. Of course Luffy would have beaten that Chinjao even faster than he did in the coloseum but that's not the point. I'm saying that in the particular final clash they had in the coloseum, if he had his drill(his attack power vastly increased with his drill and Luffy struggled a little to overcome his drillless attack), he may have won it, yet haki-wise they had equal clashes