Alun Wyn Jones is to rejoin the British and Irish Lions squad just 18 days after dislocating his shoulder.
The 35-year-old Wales lock was set for his first Lions tour captaincy in South Africa before he was ruled out by an injury in the warm-up win over Japan.
Jones has recovered quicker than expected with head coach Warren Gatland confirming he is in contention for the first Test on 24 July.
He will not play against Stormers on Saturday.
"He wouldn't be coming out unless he was coming to play, in his mind too, he feels he's back fully fit," said Gatland.
"He will arrive here on Thursday and be back in training on Monday and in contention potentially for Test selection."
Ireland scrum-half Conor Murray was named as the new tour captain after Jones suffered the injury on 26 June at Murrayfield.
Gatland believes Wales captain Jones will resume the Lions leadership role when he arrives in South Africa on Thursday.
"We will have a conversation with Alun Wyn when he gets out here," added Gatland.
"There's a big chance he will come in and be the tour captain again. We will talk to Conor and Alun Wyn and make the best decision for the team."
Jones will take part in his fourth successive Lions tour when he arrives in South Africa.
"We are delighted to welcome Alun Wyn back," said Gatland.
"It'll come as no surprise to anyone who knows Alun Wyn that since injuring his shoulder against Japan, he's done everything he can to get himself back.
"It's remarkable really when you consider it's just 18 days since he left us in Edinburgh.
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"He's been training with the Wales squad at the Vale since last week and yesterday he had a proper hit out. Following assessment from the medical staff this morning we're satisfied he's fit to return.
"He's obviously raring to go and from what I've seen on video and the feedback we've received, he's certainly not been holding himself back in training. He was really getting stuck in yesterday.
"It's a massive boost for the Lions to welcome a player of Alun Wyn's stature back."
Jones suffered the injury in the Lions' tour warm-up win against Japan at Murrayfield on 26 June, the game that also ended Ospreys and Wales colleague Justin Tipuric's involvement.
Open-side flanker Tipuric also departed with a shoulder injury.
But Jones has overcome the setback to his tour hopes to provide a significant boost to Gatland's forward and leadership resources.
The most-capped player in the game's history includes nine successive Lions Tests spanning a series defeat in South Africa in 2009, victory in Australia in 2013 and drawing with New Zealand in 2017.
When Sam Warburton was injured in 2013, Jones took over the captaincy for the decisive third Test in Sydney.
Part of his recovery included training with Wales this week as they prepared for Saturday's second Test in Cardiff against Argentina.
Jones was replaced in the Lions squad by Wales and Ospreys second-row partner Adam Beard, who has impressed in South Africa.
Beard, England's Maro Itoje, Jonny Hill and Courtney Lawes, Ireland's Iain Henderson and Tadhg Beirne are his rivals for a place in the three-Test series against the Springboks, which begins on Saturday, 24 July.
Gatland insisted Jones would not be guaranteed a Test spot.
"He hasn't had any rugby for the last three weeks, even though he's been taking a full part in training and stuff," added Gatland.
"It's something that we won't make a decision on yet.
"It's going to be a conversation about what we do with the team, because I think in the game at the moment having guys coming off the bench is incredibly important, guys who can make a difference."