As a result, De Ligt missed his first Premier League minutes of the season with a knock that is not expected to keep him sidelined for too long.
"It's a small thing,” Amorim told Sky Sports. “I expect to have him in the next game.”
Amorim added that the loss of De Ligt was a big blow considering Harry Maguire was also unavailable for selection at Old Trafford, meaning youngster Ayden Heaven was handed his first Premier League start of the campaign.
"It's hard because, if you see that position, especially this year, it's just Harry \[Maguire\] and Matta playing those positions," the Man United boss said.
"It is a blow. He is playing really really well. But I'm really excited with Ayden \[Heaven\]. He is working there. I think he has the right characteristics to play there.”
Heaven was ultimately replaced by Yoro at half time after picking up an early yellow card for a sliding challenge on Jarrod Bowen.