London - Billy Vunipola dealt the British and Irish Lions a huge blow after it was announced on Sunday that the powerhouse England backrow was pulling out of the upcoming tour of New Zealand due to a shoulder injury.
The No 8 has been a mainstay for both England in their back-to-back Six Nations title wins and in also helping London club Saracens to consecutive European Champions Cup crowns this season.
But all the while he has been trying to manage a shoulder injury.
The 24-year-old put in another mammoth 80-minute effort during Saracens' 18-16 English Premiership semi-final defeat by Exeter on Saturday, a match that turned out to be his last of the season as the reigning domestic champions fell short in their quest for a 'double Double'.
"It is really disappointing for Billy and we know how much he was looking forward to joining the squad," said Lions coach Warren Gatland in a statement issued by the combined side.
"He has been carrying an injury and feels he wouldn't be able to contribute fully to the Tour and needs further medical treatment."
The New Zealander added: "We really appreciate his honesty in making this decision and wish him luck with his recovery."
Vunipola returned to the England set-up in March for the Six Nations after four months out with a knee injury.
His place in the squad for the 10-match Lions tour, which includes three Tests against the world champion All Blacks, will be taken by England team-mate James Haskell.
However, Wasps star Haskell must first come through the May 27 Premiership final against Exeter at Twickenham unscathed before joining up with the Lions.
This would have been Vunipola's first Lions tour, with all his 34 Test appearances to date coming with England.
He had hoped to join brother Mako, the Saracens and England prop who featured in the Lions' victorious tour of Australia four years ago, on the plane to New Zealand.
Haskell had been due to tour Argentina with England next month but his call-up by Gatland leaves Red Rose boss Eddie Jones short of yet another experienced player, with 15 members of his regular squad now on Lions duty.
"We have called up James to the squad, we wish him all the best next weekend and look forward to welcoming him into camp before we depart," added Gatland.
Gatland's men leave for New Zealand on Monday, May 29, with their opening tour match just days later against a Provincial Union XV in Whangarei on June 3 as they bid to become only the second Lions side after the celebrated 1971 team to win a series in New Zealand.
This year's first Test is in at the All Blacks' Eden Park fortress - where New Zealand have not lost since 1994 - in Auckland on June 24.
Revised British and Irish Lions 41-man squad and fixtures for the tour of New Zealand in June and July after James Haskell replaced Billy Vunipola on Sunday:
Fullback/wings: Elliot Daly (ENG), Anthony Watson (ENG), Leigh Halfpenny (WAL), Liam Williams (WAL), George North (WAL), Stuart Hogg (SCO), Jack Nowell (ENG), Jared Payne (IRL), Tommy Seymour (SCO)
Centres: Ben Te'o (ENG), Jonathan Davies (WAL), Owen Farrell (ENG), Robbie Henshaw (IRL), Jonathan Joseph (ENG)
Flyhalves: Jonathan Sexton (IRL), Dan Biggar (WAL)
Scrumhalves: Conor Murray (IRL), Rhys Webb (WAL), Greig Laidlaw (SCO)
Backrows: Taulupe Faletau (WAL), James Haskell (ENG), Sam Warburton (WAL, capt), Sean O'Brien (IRL), CJ Stander (IRL), Ross Moriarty (WAL), Peter O'Mahony (IRL), Justin Tipuric (WAL)
Locks: Maro Itoje (ENG), Alun Wyn Jones (WAL), Iain Henderson (IRL), George Kruis (ENG), Courtney Lawes (ENG)
Tighthead props: Tadhg Furlong (IRL), Dan Cole (ENG), Kyle Sinckler (ENG)
Hookers: Jamie George (ENG), Rory Best (IRL), Ken Owens (WAL)
Loosehead props: Mako Vunipola (ENG), Joe Marler (ENG), Jack McGrath (IRL)
Coach: Warren Gatland (NZL)
June 03: v Provincial Union XV, Whangarei
June 07: v Blues, Auckland
June 10: v Crusaders, Christchurch
June 13: v Highlanders, Dunedin
June 17: v Maori All Blacks, Rotorua
June 20: v Chiefs, Waikato
June 24: 1ST TEST v NEW ZEALAND, Auckland
June 27: v Hurricanes, Wellington
July 01: 2ND TEST v NEW ZEALAND, Wellington
July 08: 3rd TEST v NEW ZEALAND, Auckland