WALES head coach Warren Gatland believes Ross Moriarty will bring an extra dimension his back row at the World Cup.

The Gloucester flanker was called up on Monday night after Ospreys wing Eli Walker was released due to a hamstring injury.

Walker had himself been a late call-up for Leigh Halfpenny, who faces a long spell on the sidelines after suffering a serious knee injury in the final warm-up game against Italy.

But rather than calling up another back, Gatland felt that Moriarty deserved a crack after catching the eye in the training camps and with a cameo against the Azzurri just days after being left out of the initial 31.

He will battle with Taulupe Faletau, Sam Warburton, Dan Lydiate, Justin Tipuric and James King in the back row.

"Ross was unlucky in the first place to miss out on the squad," said Gatland. "He made a huge amount of progress during his time with us in terms of where he started from in terms of fitness and a conditioning point of view.

"He hadn't had a pre-season for the last two years and he gives us a bit of X factor, and it is a great opportunity for him to get into the squad."

Moriarty's call-up does leave Wales a tad short in the back three with Hallam Amos, Alex Cuthbert and Matthew Morgan fighting for two matchday squad places alongside sure starters Liam Williams and George North.

“It’s difficult to bring someone in from the cold,” he said. "We felt we were a little bit limited in terms of bringing a wing cover in, with Tom James ruled out through injury and Eli as well.

“We have got some potential full-back options, but we just felt there is going to be quite a lot of pressure on the loose forwards in this campaign and we only have five at the moment.

“We felt strengthening that area up might give us a nicer balance for these first three games. You don’t have to swap like for like and if we do pick up an injury in the forwards then you may go to picking another back to replace him.

“There are a couple of players coming back from injury, people like Gareth Anscombe, who is going to be fit in a couple of weeks. We have got the likes of Rhys Patchell and James Hook who have also been with us too.”