Gatland will spend the next six months preparing for this summer's Lions tour of Australia, so Howley will take the Wales reins for the Six Nations.
Gatland missed most of the November internationals when the reigning Six Nations champion lost all four matches, making it seven straight defeats after being whitewashed by the Wallabies last summer.
Rees insists though that Wales fans should not be concerned about Gatland's absence.
"Rob has huge respect from the players and the coaches involved. I thought he did a great job in the autumn, although results didn't go our way," Rees said.
"Rob is an experienced coach, and there is the strength of Robin McBryde, Shaun Edwards and Neil Jenkins with him.
"Rob has got the same strengths as Warren as a coach, and it is great for us to have him.
"To be part of any Wales squad is a huge honour, and I treat this like my first one," he added.
"It's a massive Six Nations, and in terms of defending the title as well, and the Lions tour at the end of it. It's huge for all the nations."
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