London - Australia back-row David Pocock has been ruled out of Saturday's international against England, just over a day before the Cook Cup clash at Twickenham.
Pocock was in at No 8 when Wallaby coach Michael Cheika named his side on Thursday even though the loose forward was struggling with a neck injury suffered during last week's 26-7 win away to Italy.
But a further fitness test on Friday saw Pocock sidelined, a team spokesman confirmed to travelling Australian media.
Australia have yet to announce who will replace Pocock, although Pete Samu is the likeliest contender to take over at No 8.
England scrum coach Neal Hatley, speaking before Pocock was ruled out told reporters at Twickenham on Friday: "He's got double the turnovers of any other stealer in tier one this year. A hell of a good player.
"But they've got Michael Hooper and other people, (Tatafu) Polota-Nau, who jackal the ball," he added.
Saturday's match will be the final Test of 2018 for both England, coached by former Australia boss Eddie Jones, and the Wallabies.
Victory this weekend would mean Jones had won all six of his Test against his native Australia since taking charge of England following the 2015 World Cup debacle - when a defeat by eventual finalists Australia condemned the tournament hosts to a first-round exit.
15 Elliot Daly, 14 Joe Cokanasiga,
13 Henry Slade, 12 Ben Te’o, 11 Jonny May, 10 Owen Farrell
(co-captain), 9 Ben Youngs, 8 Mark Wilson, 7 Sam Underhill, 6 Brad
Shields, 5 Courtney Lawes, 4 Maro Itoje, 3 Kyle Sinckler, 2 Jamie
George, 1 Ben Moon
Substitutes: 16 Dylan Hartley (co-captain),
17 Alec Hepburn, 18 Harry Williams, 19 Charlie Ewels, 20 Nathan Hughes,
21 Richard Wigglesworth, 22 George Ford, 23 Manu Tuilagi
Israel Folau,14 Dane Haylett-Petty, 13 Samu Kerevi, 12 Bernard Foley,
11 Jack Maddocks, 10 Matt Toomua, 9 Will Genia, 8 Pete Samu, 7 Michael
Hooper (captain), 6 Jack Dempsey, 5 Adam Coleman, 4 Izack Rodda, 3
Sekope Kepu, 2 Tolu Latu, 1 Scott Sio
Substitutes: 16 Tatafu
Polota-Nau, 17 Jermaine Ainsley, 18 Allan Alaalatoa, 19 Rob Simmons, 20
Ned Hanigan, 21 Nick Phipps, 22 Sefa Naivalu, 23 Marika Koroibete