"I felt pleased for Rio. He's a good guy, with lots of experience and a real leadership quality. He's also a superb player," said Blanc.
The Frenchman revealed his influence on United's current defence during his time at Old Trafford.
"I did spend some time with Rio and Wes Brown, and maybe I was there when there was a bit of cultural change at United and in English football generally. We used to do specific drills. Alex (Ferguson) insisted that we should do more of that, but it was also true that at the beginning the players weren't especially motivated by that. They weren't so used to it," Blanc told The Times.
"I had a few ideas. In the first few sessions we had specifically on defending, I contributed some ideas. It led to improvements. At the beginning some of the players were not so keen, but we got into the habit of dedicated sessions on defending, practising different scenarios.
"I think that was of some benefit for the players, and the young players, like John O'Shea, Wes Brown, Phil Neville, and Rio, who was young but had a lot of experience. England has always had had defenders with great qualities, great commitment, but there was a time when English players did not have the same tactical training as elsewhere."
"He has such good instincts about the relationships between players, understanding how they work, knows exactly how to deal with them, how they will respond to situations."