England head coach Eddie Jones believes prop Mako Vunipola is close to becoming one of the best props in world rugby.
Vunipola, 25, has been in fine form for Premiership and European champions Saracens this season and Jones has been impressed with the player.
The Saracens forward has 35 caps to his name and is expected to be a key member of Jones’ side in the upcoming end-of-year internationals.
"He’s galloping towards becoming a world-class player," Jones told the RFU's official website.
"The Old Mutual Wealth Series is another chance for him to develop his game and he’s definitely moving in the right direction. His work rate is better, he’s fitter and he’s backing his skills a bit more."
England are unbeaten under Jones with nine straight victories and are currently ranked number two in the world rankings behind New Zealand.
However, Jones believes Vunipola is as a good as any of the New Zealand tight forwards.
"People talk about the skill-set the All Blacks have, well Mako’s got a skill-set better than all those All Black tight-forwards," he said.
"His scrummaging is consistent and you can see he’s got that thirst to be good every game. Previously he was a bit up and down, now he’s starting to get that consistency."
Jones also believes England are blessed in the front row with Harlequins prop Joe Marler returning to form along with the emerging talent of Ellis Genge.
"We are so lucky to have Mako and Joe Marler," said Jones.
"Before his indiscretion Joe was ahead of Mako and then we have a young guy like Ellis Genge. We are blessed in that area."
Meanwhile, as England fly out to Portugal for their latest training camp ahead of the end-of-year internationals Jones says lessons on player welfare have been learned from their time in Brighton earlier this month.
Sam Jones, Anthony Watson and Jack Nowell were all injured during training in Brighton and Jones says he has held positive discussions with directors of rugby at Premiership clubs.
"Out of that meeting came a couple of things that need to happen," added Jones.
"We need to communicate better with the clubs. We also need to have a better and more rigorous medical update in and out of the club and vice versa. We are committed to doing that which I think will help with player welfare."
However, Jones has defended the nature of training saying it was necessary to put the players through a high level of intensity.
"That was a camp where we needed to train with intensity to prepare for the Old Mutual Wealth Series," he said.