British and Irish Lions coach Warren Gatland says it was tough to leave out Wales centre Jonathan Davies for the tour of South Africa.

The Scarlets centre missed out to Irish duo Bundee Aki and Robbie Henshaw and Scotland centre Chris Harris.

"It was a tough call and he was absolutely outstanding in 2017 but this is four years on," said Gatland.

England duo Owen Farrell and Elliot Daly are also able to play in midfield but Gatland believes Davies still could be called up as injury cover.

"Jonathan was playing with an injury in the (2019) World Cup," said Gatland.

"He's come back and I thought we started to see some of his old form during the Six Nations but it's probably taken a little bit of time.

"It's tough but he has experience. There's no doubt we'll pick injuries up before we get on the plane to South Africa and we may get injuries out there.

"We've got players with experience who could get called up if that does happen."

Cardiff Blues flanker Josh Navidi has also missed out on back-row selection with Taulupe Faletau, Justin Tipuric, Jack Conan, Sam Simmonds, Tom Curry and Hamish Watson preferred.

"I've got a lot of time for Josh, he's had his shoulder injury and comes back in the middle of June," added Gatland

"For us, it was about looking at our loose forwards and picking a squad that we knew would be fit getting on the plane and have games under their belts.

"It was a really tough call. It's a really challenging squad. It is a good point about players being left out but if you select all those players then you'll get the same question about someone else."

One player who has been selected in 20-year-old Gloucester wing Louis Rees-Zammit who is the youngest player in the 37-man party.

"It's pretty exciting for him and I think it's his try-scoring ability and his finishing (that caught the eye)," said Gatland.

"I don't think he's the finished article and we've seen him improve during the Six Nations.

"That's what is exciting about him as a youngster. We think that going on tour, being around the best players in Britain and Ireland, then he's going to continue to develop and get better.

"There's a huge amount of potential. That's what is exciting about someone like that so we're looking forward to having the opportunity to work with him.

"We want to see him come on in a position where there are lots of options and strength in depth."