Coombs, 28, will line up alongside Ian Evans in the engine room and will win his first cap as Wales begin the defence of their 2011 title.
It’s an area of the pitch in which Rob Howley has a number of problems with Luke Charteris, Bradley Davies, Alun Wyn Jones and Ryan Jones all missing.
As a result, Coombs will be thrown in at the deep end against Ireland, but he’s determined to prove himself on the international stage.
“Emotions are running quite high,” he said. “I haven’t been sleeping much, but it’s all good isn’t it?
“It was a bit of a shock, but I’ve said previously I’ve been watching very closely.
“Unfortunately people get injured, so I just thought if it comes, it comes – if it doesn’t I just keep trying.
“I’ve been so excited since I had the call-up. I’m just really looking forward now to getting in the mix on Saturday.”