THE British and Irish Lions have suffered a devastating blow after captain Alun Wyn Jones was ruled out of the tour to South Africa by a dislocated shoulder sustained in a 28-10 victory over Japan at Murrayfield.

On the eve of the squad's departure from these shores, the Lions are coming to terms with the loss of their talisman and are now considering their replacement options at lock and skipper.

The Wales forward departed just eight minutes into the match after being hurt during a ruck clear-out by James Moore, and although he returned to the field to be with his team-mates at the final whistle, the Lions' worst fears had already been realised.

"His shoulder dislocated. We're getting it scanned but it's looking like we'll have to replace him," said coach Warren Gatland, who revealed Jones will return to Wales on Sunday.

"It's very disappointing. He's been around rugby long enough but he'll be gutted. We need to call someone in, get them PCR tested and hopefully get them on the flight tomorrow.

"The decision's pretty much made. I was speaking to the physios and they've spoken to Alun Wyn. He understands the very best case scenario is that he may get back for the Tests.

"We're discussing a couple of names at the moment with the coaches. Also potentially who will take over as tour captain. It's very, very early days for us.

"We have a leadership group that are pretty experienced and it's not something that is urgent to be done. But we are aware of who potentially steps into that role."

Maro Itoje, Owen Farrell and Ken Owens are contenders to take over the captaincy, while Jonny Gray and James Ryan are frontrunners to fill the second row vacancy.

The Lions ran in four tries against Japan in a comfortable start to their tour, but the afternoon was overshadowed by the loss of Jones and another alarming injury, this time to Justin Tipuric.

Tipuric headed down the tunnel in the 22nd minute after damaging his shoulder in a tackle and now faces an anxious wait to see if he will be fit for the tour.

"Justin got a stinger in the shoulder so we're going to check to make sure on a scan that there's no nerve damage," Gatland said.

"If there was any nerve impingement or damage then that could rule him out, but at the moment we're pretty confident he'll be OK and it's just a stinger in the shoulder."

The challenge now facing Gatland is to prevent the dire setback of losing Jones, a veteran of four Lions squads, from affecting morale.

"No one is in shock because if you're in shock its reflects back into the whole squad," said the Kiwi, who revealed that number eight Jack Conan carried a hamstring injury into the game.

"We understand things are different and fluid and we have to move on and be able to react and make decisions and that is the only way you can deal with it.

"If you go into a shock scenario and look as if you are panicking then it will reflect badly on us.

"It's disappointing for Alun Wyn and also for Justin Tipuric if he is not right, but we have to do it right.

"Let's make the right decisions and do it as quickly as we can in the calmest way that we can."