The former Blackburn Rovers defender saw his transfer to United rubberstamped yesterday.
Smalling said: "It should have been difficult for Phil with his move to United still going through but you wouldn't have thought it, would you? He was excellent.
"We've trained and played well together in the last couple of weeks.
"The move won't change that and our togetherness showed right until the last minute against Spain and I'm sure it will benefit us in the future."