The former Manchester City youngster made his Three Lions debut with an eye-catching cameo off the bench in the goalless draw against Croatia on Friday, becoming the first player born after the millennium to play for England in the process.
Sancho is now in line to make his full debut in Monday's UEFA Nations League clash against Spain in Seville and when asked about his club team-mate, Witsel had only positive words for the starlet.
"He's really talented, he's fast, technical and a good guy also," he enthused.
"With us [Dortmund] he's doing really well. I think if he stays like this and keeps working hard he can become one of the best wingers in the world."
Meanwhile, Witsel also gave his thoughts on Thierry Henry's decision to leave his role with Belgium to become Monaco's new boss, saying: "It's sad for us. But I think everybody knew before that Thierry wanted to be a coach. This is football and we are happy to have had him for two years.
"He brought a lot of experience, he was close to the players and speaking all the time with us. I think now he is ready and it is the right time for him to be a coach."