The on-field clash between Morrison and team-mate Wilfried Zaha soured the young Lions’ 5-0 victory over Lithuania at Portman Road on Tuesday night, with the pair having to be separated by midfielder Nathan Redmond.
And Southgate, who took the England post in August, fears a lack of unity in the dressing room could hinder the progress of his starlets.
“We spoke about being a team before the game,” he said.
“We know the potential of the group of individuals. The key now is how we come together as a team and that will take time because there is a lot of focus on individuals.
“It’s my job to bring them together as a group, which is going to be a test as I can see.”
Morrison, a troublesome but supremely talented midfielder, was allowed to leave Manchester United by Sir Alex Ferguson 18 months ago in the hope he could be tamed by Sam Allardyce at West Ham. The 20-year-old has nailed down a regular starting berth this term and scored a superb solo goal in this month’s 3-0 win at London rivals Tottenham.
The 20-year-old is now being tipped as an outside bet to make the senior World Cup squad.
Morrison had struck twice to help England build a 4-0 lead but was angered after being denied the chance to complete his hat-trick when Saido Berahino instead took a late penalty.
He was soon confronted by Manchester United’s Zaha while the game was in full flow and arms were raised, but peacemaker Redmond was keen to play down the incident.
“It was just a bit of a disagreement, nothing else,” said the Norwich midfielder.
“We got back in the changing rooms and we sorted it out. Rav’s a class player, sometimes he just has to move the ball a little bit quicker.
“Sometimes you do get a little bit frustrated with him, but you just have to let Rav be Rav because of the things he is capable of. You get it with teams everywhere. There is just a bit more of a spotlight on this incident because it was for England.”