Casemiro opened the scoring in the 3-1 win at Old Trafford. Both the club and the Brazilian veteran have announced he will leave this summer as his contract runs down.
Asked about a U-turn, Carrick said afterwards: "I think, in some ways, it’s difficult to say, I think when something is decided, in some ways, the fact that it’s decided makes things a little bit easier and everyone understands the situation really.
"I think the impact he’s had has been terrific, certainly since I’ve been here and working with him, and his influence in the team and big moments in goals.
"And I think it was a nice moment at the end there with the supporters, and having that connection and the respect. That was a nice moment and I think he’ll enjoy that."
The Geordie also said: "Listen, this is totally no disrespect to Case, he’s been fantastic, he’s been a player for us and he’s been important in the dressing room and one that I’ve spoke to and connected with really well.
"But as a club and as a team, players come and go, some are bigger, some are maybe more important than others at different times, but I don’t think it’s ever really about replacing like for like, I think you can go in a different direction, you understand what the balance of the squad needs, whether that’s on the pitch, off the pitch, leadership, positionally - there’s all sorts of different things going into it.
"Case has done some really, really good things, certainly since I’ve been here, he’s been an absolutely pleasure to work with."