Sir Alex Ferguson admits several players, including Nani and Ashley Young, were left disappointed by their omission against Real Madrid.
Both Nani and Young failed to make the bench for the Champions League last-16 encounter at the Bernabeu on Wednesday, which ended in a 1-1 draw ahead of the second leg at Old Trafford in three weeks' time. The snub struck another blow to out-of-favour Nani, who was fallen down the pecking order at United to fuel talk of a summer exit.
Ferguson admits it was a tough call to make, saying in the Daily Express:
"There were a lot of disappointed players. "Nani and Ashley Young - international footballers - I found it hard to explain to them I was leaving them out."
Another player to miss out was unused substitute Javier Hernandez, with Ferguson preferring top scorer Robin van Persie up front, with Wayne Rooney in a deeper role.
But the boss says chances will come for the Mexican frontman, nicknamed 'Chicharito'.
He added: "I explained to Chicharito that Robin van Persie is our main striker and we wanted someone to join in from a deeper position.
"Whenever Chicharito plays, he delivers. He has 14 goals, he will score more than 20 and will have opportunities."