Man Utd were set up to frustrate us and Mourinho did what he's known for. Can offered some physicality in the middle as it was a war of attrition at times. He was rusty, and a bit slower to pass, which was understandable. Arguably Wijnaldum would have kept it all moving a bit faster and we'd have played around them better, but it's hard to say if that's what would have happened. Sturridge was also dropping deep so it was getting packed in the middle there, and Firmino was peripheral before he moved to the middle. When Lallana came on we had a better tempo too.
In other words, there were several factors at play as to why the performance was like that. Missing Wijnaldum was only one factor. I think the biggest factor was Mourinho and his determination to send out a team to stop us, rather than do much of anything themselves.
Frustrating and small time as it is, we'll learn from that.