Andre Villas-Boas suffered the biggest home defeat of his reign as Tottenham manager on Sunday evening as West Ham ran riot, claiming a fine 3-0 victory in north London thanks to three goals in 13 second-half minutes.
Ricardo Vaz Te doubled West Ham's lead after Winston Reid's opener and Morrison then brought the away fans to their feet with a fantastic solo goal.
The former Manchester United man picked the ball up inside his own half and slalomed past Jan Vertonghen and Michael Dawson before cleverly lifting the ball over Hugo Lloris.
West Ham had struggled without the injured Andy Carroll so far this season, but Morrison performed admirably up front, much to Allardyce's delight.
"That was a genius goal," the West Ham boss said.
"Tottenham had conceded two goals before today, but he just headed directly to Vertonghen and Dawson, slipped them like they weren't there and he used his outstanding ability to dink the goalkeeper.
"For me you will struggle to see a better goal this season."
Many questioned Allardyce's decision to sign Morrison from United last year."
The midfielder was convicted of two counts of witness intimidation and he was also fined £7,000 by the Football Association for a homophobic tweet.
The player failed to settle originally at West Ham and was loaned out to Birmingham last season.
But 12 months on, Allardyce says the 20-year-old is a changed man.
"The penny has dropped with him," Allardyce added.
"It has dropped in lifestyle and attitude and his timekeeping, all of a sudden there is a belief that he doesn't want to do anything other than break into our first team.
"I think that 12-month spell at Birmingham gave him a time to reflect on what it takes to be a player on a week in and out basis."
Allardyce revealed that former United boss and close friend Sir Alex Ferguson told him he was getting a potential star when he signed Morrison in a deal that was reported to cost the London club just £1million.
The West Ham boss said: "When I signed him Sir Alex said 'I hope you can sort him out because if you can he will be a genius'.
"He needed to get away from Manchester and start a new life and it looks like it is paying off for us.
"The fans at Tottenham today thought it was going to be a nice easy breeze today, a nice comfortable three points.
"But the Premier League will tell you that if you think like that you are going to get your backside kicked and they got their backside kicked today."
A shell-shocked Andre Villas-Boas looked like a man who had just had his backside kicked when he sat down to sum up his feelings after the game.
Tottenham had only conceded two goals prior to today's game, but Andros Townsend looked the only player capable of making a difference for the north London club and the fans who were left inside the stadium at the final whistle made their feelings known by booing the team off the pitch.
Villas-Boas, who had claimed four wins from six games prior to the derby, called for a bit of perspective, though.
"It's a wake up call that we have to react to, we have to bounce back and I trust the team to do that," the Spurs boss said.
"I think we can't undermine what we have been doing up to now.
"Obviously it's a defeat. Had we won this game we would have been just one point behind.
"It's something we don't like, but we have to put into perspective of what we've done before."