He has also played a key role in Ulster reaching the quarter-finals of the European Cup and he was among Ireland's stand-out performers in their autumn internationals.
Against South Africa and Argentina he won his third and fourth caps, having first been capped in Australia in 2010 but ultimately Sean O'Brien and Peter O'Mahony have been given the nod at flanker.
But Kidney revealed it was far from an easy decision.
"We felt that in terms of a mix in the back row this was the best combination, but there was certainly plenty to talk about following Chris' performances in the autumn," he said.
"I would have to say I have never come across an easy dropping yet, but the lads all stand up to it. It can be a tough job but this morning the players who didn't make the cut probably trained better than the guys that did.
"Every player looks for an opportunity and that is what these players have now. The way they are training, they are going to go and grab it with both hands."
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