Wales defence coach Shaun Edwards says protecting Matthew Rees' long-term health outweighed all temptations to select the captain for the World Cup.
Hooker Rees, 30, has failed to overcome a neck injury and has followed medical advice to have surgery, ruling him out of rugby's showpiece event.
"It's obviously, from a rugby point of view, incredibly disappointing to lose your captain," said Edwards.
"But there are more important things in life than rugby."
Rees' chances of making the World Cup squad were rated at 50-50 by coach Warren Gatland on the eve of Saturday's second warm-up match with England.
Gatland had hoped to delay the need for surgery until after the World Cup in New Zealand, but the severity of Rees' injury has now become clear with the Wales medical staff fearing long-term and permanent damage if the hooker attempted to play through the pain.
Edwards revealed the injury had changed Rees' whole demeanour and acknowledged that the correct decision had been taken to air on the side of caution.
"Matthew's in such pain at the moment that [rugby] has to be secondary to his life," added Edwards.
"If you see Matthew Rees normally, he's always got a bit of banter and is laughing and joking. But at the moment he's walking around like he's not Matthew Rees because he's in such pain all the time.
"That ruins your life so he has to take the doctors' opinion and has to get it done because you can't live your life in such pain like that.
"We're all gutted he's not going to the Rugby World Cup and leading us, but just to see him back living a normal life without pain is the important thing.
"He's in agony. He can't sleep. He's just constantly in agony."
Sam Warburton has captained the side in Rees' absence for the last three Tests.
The 29-year-old will be out for "six to eight weeks" after having corrective surgery, casting major doubt over the centre's involvement at the World Cup.
Henson, who missed out on selection for the two previous World Cups, said he rejected an offer to stay with Toulon in order to chase his dream of playing at this tournament.
"To say I'm gutted for him is the understatement of the century because he'd worked very hard and made sacrifices," said Edwards.
"He's just had such bad luck with injuries hasn't he. I couldn't be more gutted for a player.
"I thought he and Jamie [Roberts] were looking pretty awesome together, particularly in defence.
"That first hit on [Matt] Banahan and carrying him back 30 yards... but unfortunately he just gets injured again. It just seems that fate is not helping him."
Wales, who have added Richard Hibbard to the squad to cover Rees' withdrawal, will play Argentina in Cardiff on Saturday in their final World Cup warm-up match.
Warburton will be rested, with Martyn Williams set to play at open-side, while prop Adam Jones, full-back Lee Byrne and wing Leigh Halfpenny are fit for selection after missing the two previous games.
The fitness of Stephen Jones, Rhys Priestland, Ryan Jones and Gethin Jenkins was being assessed on Monday before the team is announced at 1230 BST on Tuesday.