The Red Devils had a few nervy moments but finally overcame the Cobblers 3-1 at Sixfields Stadium to progress to the fourth round of the league cup.
"We deserved it. It was as I was expecting," he told Sky Sports and MUTV.
"We were totally in control for the first 35 minutes and then we were back in control for the last 25 minutes.
"As a team we had control from the beginning. I think the substitutions were just a contribution and, overall, the team was completely in control.
"The game could and should have been easier, because normally it is easier against 10 men – we should have been playing against 10 men very early in the second half. But they fought and they played with their strength.
"They tried to cause us problems, which they did at times, so it was a difficult match but overall it was a positive performance."
United will next meet local enemies Manchester City in the next round of the cup at Old Trafford in the week commencing October 24.