England coach Eddie Jones has hailed Wallabies flanker Sean McMahon as a quality player but warns his direct opponent in Saturday's second Test Billy Vunipola is ready to play the game of his life in Melbourne.
McMahon will replace the injured David Pocock at No.8 for the clash at AAMI Park, which Australia have to win to remain alive in the three-Test Cook Cup series.
Capped seven times at international level, the 21-year-old represents one of the biggest selection gambles of coach Michael Cheika's short tenure.
McMahon has limited experience in the No.8 role and gives away a whopping 26kg on Vunipola, the English vice-captain, but Cheika believes his aggression, workrate and attacking abilities will more than make up for it.
Jones, however, isn't so sure.
"I don't know how McMahon will go but I know how Billy's going to go. He's ready to play the game of his life," he told reporters on Thursday night after unveiling England's team.
McMahon became the youngest player to represent Australia in rugby sevens back in 2011 but joined the Melbourne Rebels four years later to be a consistent threat in Super Rugby since.
Jones remembered watching McMahon play for Australia one year at the Tokyo Sevens and said he was clearly the best player there.
"He stood out by a mile. McMahon's a good player - he's always impressed me," he said.
"A couple of years later, he's playing for the Melbourne Rebels. He's done well for them.
"He'll add to the Australian side."
Jones said earlier in the week England were preparing as if Pocock would play in Melbourne, suggesting his fractured eye socket was a selection smokescreen by the Wallabies.