Louis van Gaal was frustrated by what he deemed "an unnecessary loss" for Manchester United against West Brom in the Premier League.
United suffered a 1-0 defeat at the Hawthorns on Sunday, with Salomon Rondon's second-half strike punishing Van Gaal's side, who had Juan Mata dismissed in the 26th minute following two yellow cards in quick succession.
The Dutchman felt the red card was the decisive factor in the game and was embittered by seeing his team suffer what he deemed an undeserved reverse.
"For us it's a very bad moment, and it was in my opinion an unnecessary loss," Van Gaal said. "I don't want to say that we deserved to win, but we didn't deserve to lose.
"When you see at the end of the game the chances they have created in comparison with us, it was an unnecessary loss.
"When it is a draw and you play 60 minutes with 10 men you can accept it, but now you lose and you lose contact with the first four or five.
"We played 60 minutes with 10 against 11 and that's always difficult, but we were not uncomfortable. We didn't give too many chances away in the second half, were well-organised, but it's difficult to create chances with 10 against 11.
"The [red card] decision was, for us, the turning point in the match."