Depay was dubbed as one of the best Dutch talents before securing a move to Old Trafford from PSV Eindhoven in 2015, where he scored 39 goals in 90 league matches.
The Dutchman could not replicate his previous form with the Red Devils, scoring only two goals in 33 Premier League games.
Manchester United sold the then 23-year-old in January 2017 to French side Olympique Lyon less than two years after acquiring his services.
Speaking ahead of the Netherlands’ crucial EURO 2020 qualifier against Northern Ireland on Saturday, Koeman opined that Depay moving to the Premier League in 2015 was premature as the 25-year-old was “a little bit too young’.
"I think he's a top player and maybe during his time at Manchester United he was a little bit too young," Koeman told reporters.
"He's now more experienced and what he's showed and what he has done for the national team is great and I'm really glad that we have that kind of player in our national team.”
Depay has blossomed since making the move to the Groupama stadium in 2017 and he has emerged as one of Lyon’s best players despite their troubled start to the season.
His impressive form has seen him linked with a move back to Old Trafford while Tottenham Hotspurs are also reportedly keeping tabs on the 25-year-old.
Depay has scored seven goals in 10 Ligue 1 games for Lyon this season and he has four goals in as many UEFA Champions League games.
