The Brazil international was linked with a potential move away from the Serie A champions in the summer after the 28-year-old fell down the pecking order during the 2018-19 season.
Sarri was appointed as Massimiliano Allegri’s replacement at the Turin outfit after the Italian coach led Chelsea FC to a third-placed finish and the Europa League crown.
The new Juventus manager decided to retain Costa’s services despite the former Bayern Munich midfielder making a measly seven Serie A starts in the previous campaign.
Costa has made a decent start to life under Sarri so far to help Juventus ease to victories over Parma and Napoli in their opening two Serie A fixtures.
The Juventus winger’s agent Giovanni Branchini has claimed that Manchester United had a “strong interest” in Costa this summer – but Sarri didn’t want the Brazilian to leave.
“I sincerely say that Allegri and Sarri have never thought of letting him go,” Costa’s agent Branchini told the Daily Mail, as quoted by Metro.
“The interest of Manchester United was strong, a club that has always been interested in the Brazilian.
“It was not the only club but in England it was certainly the most active team on the trail of Douglas Costa.”
Manchester United ended up signing Swansea City winger Daniel James, Crystal Palace full-back Aaron Wan-Bissaka and Leicester City defender Harry Maguire in the summer transfer window.
The Red Devils have collected five points from their opening four games in the Premier League so far this season.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news