Wales back-row Josh Navidi is out of the World Cup with a hamstring injury.

Coach Warren Gatland said he will draft in a back to take the Cardiff Blues player's place in the squad.

Centre Jonathan Davies missed the quarter-final win over France for Gatland's side, who face South Africa in Sunday's semi-final in Tokyo.

"Given that we've got six back-rowers and we've got five fit at the moment, we've been a little bit short in numbers in the backs," said Gatland.

"So it probably will be a back who comes out as a replacement."

The Wales coach said Navidi's injury is "a grade two hamstring so it's at least a couple of weeks [out]".

Gatland added: "It's disappointing for him. Hopefully we will keep him out here.

"Obviously he loses his accreditation, but since he's gone so far in the tournament it will be nice for him to stay out for the next couple of weeks. We're just going through that with him.

"It's very disappointing for him as he's been very influential and important for us in the last year.

"It's disappointing to have a player ruled out, but in saying that these games are so physical and to have only one player ruled out at this stage is a real positive for us."

Wales have strong back-row options, including Ross Moriarty, who came on to replace Navidi when he went off injured in the first half against France.

Navidi had overtaken Moriarty as Wales' number eight choice for the tournament while Bath's Taulupe Faletau was ruled out in the summer because of a collarbone injury that needed surgery.

The 28-year-old Navidi has also played at open-side and blind-side for Wales since his debut in 2013.

Moriarty and Aaron Shingler are similarly versatile while Aaron Wainwright, who scored a try against France, can also switch back-row roles.

However, Wales have only three centres in Japan, Davies, Hadleigh Parkes and Owen Watkin.

Ospreys' Watkin started alongside Parkes, who has played in every Wales match at the World Cup despite breaking a bone in his hand in the opening win against Georgia.

Ospreys centre Scott Williams was part of the extended pre-tournament training squad, as was Cardiff Blues wing Owen Lane, and both those players could be contenders to take Navidi's place in the 31-man party.

Gatland has yet to decide and said he had "a number of options" but said "yes" when he was asked if he was confident Davies and Parkes will both be fit to face South Africa.

"He [Davies] has been doing his rehab and recovery so hopefully he will be up and running for training tomorrow [Tuesday]," Gatland added.

"Hopefully he will be fit and available.

"We missed his experience last night [against France]. Owen Watkin is a player for the future, he's a quality kid and has been great for us off the bench. He did well up against two big, physical French centres.

"In the end the difficult decision with Jonathan was going into the game with two midfielders who weren't 100%.

"Hadleigh still has a broken bone in his hand, and had a shoulder contusion from the last game. He was carrying that. To have one centre [playing] that was fit was pretty important."

Wales go into Sunday's semi-final hoping to reach the first final in their history.

Wales finished third at the inaugural 1987 tournament and fourth in Gatland's first tournament in charge in 2011.

The Springboks ended Wales' interest in the quarter-finals at the 2015 event hosted by England.

Navidi is the second Wales player to leave Japan with lock Cory Hill having departed without playing a game having failed to recover from a stress fracture in a leg.

Dragons' Hill was replaced by Ospreys' Bradley Davies while another Ospreys lock, Adam Beard, arrived late after recovering from appendicitis.

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All pictures via Huw Evans images