Walsall's Adam Chambers was unlucky to be sent off against Middlesbrough, according to manager Dean Smith.
Midfielder Chambers was dismissed after 12 minutes by referee Darren Deadman for a two-footed challenge.
"I do think it was harsh. Yes, he goes in with two feet, but his sole intention is to get the ball and he takes the ball," Smith told BBC WM.
"Letter of the law, you can give him a red card. Spirit of the game - he's not hurt the lad, there's no intent."
Walsall went on to lose the Carling Cup first round tie 3-0 at the Banks's Stadium, Marvin Emnes scoring a hat-trick that was completed by a disputed second-half penalty.
It is the fifth year in succession that the Saddlers have fallen in the opening round of the competition, although Smith feels Chambers' dismissal made that exit inevitable.
"I certainly think it was a turning point in the game. They're a very good Championship team in a strong league this year.
"It was going to be hard even 11 versus 11, but 11 versus 10 was a bridge too far for us.
"I think there should be more leniency and understanding about whether a player's trying to hurt somebody or not.
"Chambers was committed to the challenge, he's gone low, unfortunately for him he goes with two feet."
The midfielder will now serve a three-match suspension with another summer signing, Anton Peterlin, in the frame to make a start at Hartlepool on Saturday.