The defensive end has been touted to go to the Texans first overall, but due to the quality of defensive players the club already have, McNair is unsure what would be the best outcome for his side with many willing trade partners.
He told Fox Sports: "You take a guy like Clowney. He's obviously the best player in the draft, but he's a defensive end. He's not a quarterback. If he's a quarterback and the best player it's easy, but that's not the case.
"So can that defensive player have a greater impact on the success of your team than one of these quarterbacks? It's not a sure thing that he is.
"If somebody wants you to drop down and they give you two or three more picks that would let you get two or three more quality players, are you a stronger team dropping down a little bit, getting these additional picks and getting more depth?"
The Texans finished with a 2-14 record in the 2013 season.