But Borussia Dortmund wing-back Ian Maatsen has been left out of the final 26-man squad despite his strong performances helping to propel the German club to this Saturday's Champions League final against Real Madrid.
Depay has scored 44 goals for the Oranje and is closing in on Robin van Persie's all-time leading goal tally of 50. De Jong's control and surging runs from midfield are considered vital to the success of the Netherlands team.
Koeman said De Jong would join the squad on Saturday "and then we'll have a better picture (of his fitness), but it's going well." He said he expects De Jong will be fit to start against Poland, though it is not yet clear if he will be able to play the whole match.
The coach said that he is cautiously optimistic about the Netherlands' chances in Germany despite a number of injuries, particularly to his midfield.
"We have a team that is hard to beat," Koeman said. "We have a lot of creative quality in the forwards, so I think we have a strong team."
Maatsen was one of three players Koeman dropped from his provisional squad, alongside Sparta Rotterdam goalkeeper Nick Olij and Feyenoord defender Quinten Timber, who misses the tournament because of an injury.
Although he has never played for the national team, Maatsen's strong performances since joining Dortmund on loan from Chelsea had put his name in the mix for a place in the squad for the June 14-July 14 tournament. His omission leaves Koeman without a genuine left back in his squad. He said veteran Girona defender Daley Blind or Micky van de Ven of Tottenham could play in that position.
NETHERLANDS SQUAD FOR EURO 2024
Goalkeepers: Justin Bijlow (Feyenoord), Mark Flekken (Brentford), Bart Verbruggen (Brighton).
Defenders: Nathan Aké (Manchester City), Daley Blind (Girona), Virgil van Dijk (Liverpool), Denzel Dumfries (Inter Milan), Jeremie Frimpong (Bayer Leverkusen), Lutsharel Geertruida (Feyenoord), Matthijs de Ligt (Bayern Munich), Micky van de Ven (Tottenham), Stefan de Vrij (Inter Milan).
Midfielders: Teun Koopmeiners (Atalanta), Frenkie de Jong (Barcelona), Ryan Gravenberch (Liverpool), Tijjani Reijnders (AC Milan), Jerdy Schouten (PSV), Joey Veerman (PSV), Georginio Wijnaldum (Al Ettifaq).
Forwards: Steven Bergwijn (Ajax), Brian Brobbey (Ajax), Memphis Depay (Atlético Madrid), Cody Gakpo (Liverpool), Donyell Malen (Borussia Dortmund), Xavi Simons (Leipzig), Wout Weghorst (Hoffenheim).
