Manchester United gave the clearest indication yet of their transformation under Ole Gunnar Solksjaer by hanging on to defeat Tottenham Hotspur at Wembley.
Marcus Rashford scored the only goal, latching on to Paul Pogba's fine through ball to finish low past Spurs keeper Hugo Lloris.
But the real architect of United's sixth successive victory was David de Gea, who pulled off a string of saves to deny the hosts as they piled on the pressure in the second half.
Tottenham also had a Harry Kane effort ruled out for offside before Rashford gave United the lead.
Spurs, third in the Premier League, have now lost back-to-back top-flight home matches and are nine points behind leaders Liverpool.
United have won every game since Solskjaer replaced Jose Mourinho in December and have joined fifth-placed Arsenal on 41 points, six behind Chelsea in fourth.