Morrison was shown a yellow card by referee Lee Mason for raising his hands to Joel Ward in an incident sparked by James Tomkins, who inadvertently kicked the ball at the Palace defender in frustration over the loss.
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"I haven't really seen it, I've been told that there was a little bit of an incident but I haven't really seen it so I wouldn't like to comment," West Ham assistant manager Neil McDonald told reporters.
"But that's his fifth booking now, so he's suspended for the next game which is more disappointing than anything else really."
McDonald suggested that Morrison's previous cautions may also have been avoidable.
He added: "I think he's had another four bookings where he can possibly not get them and this one is out of frustration really that we haven't got anything out of the game, and not just him but the rest of the players are very, very disappointed that a couple of decisions have gone against us and we've lost the game."
West Ham manager Sam Allardyce did not attend Tuesday night's press conference after the defeat at Selhurst Park out of frustration over seeing Stewart Downing's goal disallowed in the second half.
"He's still a little bit livid after the performance today, not just of our players but of the officials as well," McDonald said.
"We feel a little bit hard done by, especially [with] the goal that we scored. It was given to be a foul and that really stopped us from getting back into the game and possibly going on to win it."