David De Gea was flattened by an X-rated challenge by the on-loan Liverpool striker at the end of the first half, which the boss believes warranted a red card. However, referee Lee Probert did not even deem it a bookable offence, although he did later caution Carroll following another tussle with the keeper.
Nemanja Vidic was also caught by a stray elbow from the Hammers' star man and was clearly still unhappy with the challenge as he left the field at the end.
Sir Alex is proud of the way his players responded and had words of praise for De Gea, who has been subjected to some untidy aerial challenges in recent weeks.
"We know how they play," said the manager. "The ball is in the air most of the time and you have to defend those things. They were very aggressive as you’ve seen tonight.
"There’s no doubt it’s a red card [for the challenge on De Gea]. It’s obvious. The referee saw it differently. We’re looking for players to be protected and didn’t get that.
"David has been improving all the time and is developing into a fantastic keeper. It’s just a matter of experience in the English game – he’s got stronger. His training performances are really good and he’s shown that again tonight. As we’ve been saying for quite a while, he’s developing into a first-class goalkeeper.
"Vidic has a badly bruised jaw [area] but I don’t know what happened in that situation.