Koeman named 30 players as part of his provisional squad last week, with that number now cut down to the 26 players required to satisfy UEFA regulations for the tournament.
While one of the decisions was relatively straightforward – former Middlesbrough midfielder Marten De Roon has been ruled out of the tournament through injury – the ex-Barcelona boss still had three tricky calls to make.
In the end, Koeman decided to cut fourth-choice goalkeeper Nick Olij and Feyenoord midfielder Quinten Timber from the final squad.
Ian Maatsen was the most surprised player dropped,
The attack-minded defender, who is on loan from Chelsea, has scored three goals and assisted two more since arriving at Signal Iduna Park in January.
Koeman has opted for Nathan Ake, Daley Blind, Lutsharel Geertruida and Micky van de Ven as his left-back options, with Jeremie Frimpong and Denzel Dumfries likely competing for a spot at right-back.
Speaking in his press conference after the squad was announced, meanwhile, Koeman made a extremely blunt comment about how difficult his decisions were.
He said: “I Facetimed Ian Maatsen this morning. Was it difficult? No. This is my job. I know these moments are coming.”
The former Everton and Southampton boss was slightly more forthcoming when it came to detailing Maatsen’s omission: “I had to think about when to tell Ian Maatsen my decision because he still has to play a Champions League final,
“I thought this morning was the right moment to tell him, because he would still have three days left to focus on the final He is disappointed.”
