Morrison revealed that West Brom's players were fired up by suggestions they would slacken in the last two games following Roy Hodgson's appointment as successor to Fabio Capello.
He said: "It was a talking point before the game and we knew people would have been saying that our season is over.
"We wanted to send him off on a high because he's a great bloke and a great manager.
"He was building something here. Thanks to the gaffer and his knowledge, we've progressed from last season.
"You can't argue with the job he's done and we wish him all the best."