Phil Jones' performances in recent weeks have surprised Manchester United manager Jose Mourinho after a lengthy spell on the sidelines due to injury problems.
The 24-year-old missed the majority of last season and was also absent during the opening stages of 2016-17 due to a knee issue.
Jones has been a regular starter of late, though, forming a defensive partnership with Marcos Rojo, and Mourinho is pleased with the duo.
"I am surprised how Jones has coped because, even with me, he had this injury that stopped him for a long time," Mourinho said at a news conference on Monday to preview United's Premier League clash at Crystal Palace in midweek.
"He was recovering first with people he trusts in the medical department.
"Then he was working hard with one of my guys for a few weeks before he joined us, and he had a big improvement in his physical condition.
"Now he looks fresh, and strong, and fast and agile. He has played six matches and I do not remember the last time he did that.
"Marcos also had lots of problems and injuries, but he looks also free of it.
"In a period without [Eric] Bailly and [Chris] Smalling, where people could be scared, they step up and both played so many matches already without defeat. I am really happy for them. They have done very well.
"Now we have a third central defender to rotate, like we gave a rest to Jones in Ukraine [for the Europa League tie against Zoyra]. Now Jones played against Tottenham free of injuries or tiredness. So now we have a third central defender, so until the end of the year, hopefully we can manage with those three in those two positions."
Mourinho faced the media shortly after United were paired with Saint-Etienne in the first Europa League knockout round, with Paul Pogba due to face his brother Florentin.
"That is a nice thing. Paul was already laughing and for sure his brother is also laughing. It has happened in the history of football a few times and it is nice," Mourinho stated.
"Then Saint-Etienne. It is a historical club with lots of tradition. People of my generation never forget that [Michel] Platini team. And it will be difficult because every team that is left in the competition is a good team.
"For sure, Man United are one of the big names in the competition, but it will be hard."