The former Ospreys centre cum fly-half made his return to the Wales team during the summer Tests following a 19-month sabbatical from the game but fractured his wrist during the win over England and was subsequently ruled out of the World Cup.
Jamie Roberts, Jonathan Davies and Scott Williams all impressed in Henson's absence in midfield, while Rhys Priestland joined James Hook and Stephen Jones in wearing the No10 shirt.
So with an array of riches at 10 and 12, Gatland has made it clear that reputation alone will not secure Henson a starting spot for the World Cup semi-finalists.
"Gavin just has to play well for the Blues, whether that is at 10 or in the midfield," Gatland told the Western Mail.
"But I think the main challenge for him will be how good our midfield was in New Zealand.
"Probably the unsung hero was Scott Williams. I have a lot of time for him, he is very talented. He has great footwork, physically he has a presence and he has a good boot on him.
"So for Gavin to come back in it's not going to be a case of him just having a couple of good games and being automatically selected.
"He's no mug and he will know that anyway. His injury before the World Cup was very unfortunate, and he was playing well before it happened. But it also gave us a chance to unearth others and I think we did that."