After 11 years with Saracens, Vunipola, 31, joined the French Top 14 team this summer.
Because the Rugby Football Union forbids players stationed overseas from being chosen for England, the transfer prevents him from adding to his 75 international caps.
“I’m probably in better shape than I’ve ever been in the last two or three years,” Vunipola, who battled injuries in his last few seasons in England, said to Rugbyrama.
“I am to blame for this; my former club is not to blame. As previously stated, upon arriving here and learning about the surroundings,.
Vunipola earned his final cap off the bench during England’s World Cup semifinal loss to South Africa last year. He made his debut for his nation in 2013 against Argentina.
He spent most of his club and international career playing alongside his brother Mako, and the 26-24 triumph over Vannes, his brother’s new team, on Saturday was a “strange” occasion for the two of them.
Billy Vunipola added, “I think the distance has brought us closer, knowing that he’s not there all the time.”
