Ralf Rangnick considered switching to a back three after Manchester United went 2-0 up at Aston Villa but feared it would have sent the 'wrong signal' to the players.
Bruno Fernandes struck his second of the game to give United a two-goal cushion following a mistake by Morgan Sanson when Villa had been threatening to equalise in the first 20 minutes of the second-half.
None of the United substitutes warmed up amid Villa's dominance until just after the hour mark and Rangnick eventually turned to Jadon Sancho at 2-0.
Sancho emerged in the stoppage after Jacob Ramsey scored in the 77th minute and the United winger was careless in possession. Fellow substitute Philippe Coutinho pounced in the 82nd minute to earn Villa a deserved draw.
Rangnick made a double change with the introductions of Donny van de Beek and Jesse Lingard in the 89th minute but by then United seemed resigned to dropping more points in the Premier League.
"I mean, obviously after we scored the second goal I was thinking of a back three," Rangnick explained. "But my worry was that if we did that we would be pinned back too much, in the end it still happened. If I could do it again I would probably change to a different formation, to a back three.
"After being 2-0 up, it might have been a wrong signal to the team to drop too far back and when we played proactive today we pressed them and were able to put them under pressure and had our best moments today.
"We were 2-0 up after 77 minutes and had 15 minutes to play and in most parts of the game we were compact, we could defend in the midway block, but in those 15 minutes we conceded two goals in four minutes. I haven't seen them on video but they were both similarly prepared and happened in a similar way.
"I think we had quite a few positives today. In the first half-hour we dominated the ball, we also kept them away from our own box, in the first 30 minutes we didn't concede one single shot on our goal.
"But again, it's about playing in that way and as compact as we did in the first half-hour and in parts of the second-half but have to do it in a longer period of time, so right now it definitely feels like two lost points, and it almost feels like a defeat, to be honest, after being 2-0 up.
"For me, it was one of the best performances since I came here six weeks ago. We controlled the game in the first half-hour completely, we could've been two or 3-0 up. In the second-half, we had our moments, played well and when you are 2-0 up after 70 minutes you have to take the three points and this is what we didn't manage to do in the end.
"I don't think we were panicking but we were not as compact as we were in most other parts of the game and that's why the two goals we conceded were too easy for them to dribble and pass through our lines, and this is what we did well in other parts of the game but didn't do it well in the last 15 minutes."
