Morgan's Magic Snowplow said:
I think its mostly just horrible execution by Spurs. United might have surprised them by pressing more than usual and dropping a forward more into midfield but its nothing the players haven't seen before and United isn't particularly effective in pressing, given their lack of quickness up front. And LVG has been using knockdowns to Fellaini as the squad's primary outlet when in possession for months now.
Possession before the sub was 63-37 Man Utd. Possession since is 55/45 Spurs. Some of that is score effects but the tactical realignment has made a big difference.