The Dons were reduced to ten men in the 18th minute of the Scottish Cup semi-final - the Hoops winning 4-0 - when the centre-half was given his marching orders for a challenge in the box and both managers have said they feel the decision was harsh.
"I think a lot of managers would like to see 11 versus 11 where possible," said Brown.
"Certainly the penalty alone is a harsh punishment but not only do we lose the player for that game, we lose him for another game, for that one challenge. It's pretty harsh."
"And the same player was sent off in two minutes at Pittodrie against Celtic which left us a man short again," he added.
"I think it is a harsh rule but that is the law of the game and we have to abide with it.
"I don't know whether (Gary) Hooper was certain to score and if he wasn't then we could feel aggrieved.
"But I have very good respect for Willie Collum so we have to accept the decision.
"However, it made it an uphill task for us.
"To play against the best passing team in the country a man sort is very difficult.
"But you have to concede that Celtic were the better side."