The 21-year-old may have conceded three times in the reigning Premier League champions’ visit to Stamford Bridge, but two heroic saves in stoppage time, denying Juan Mata twice, ensured a draw for the Red Devils.
Sir Alex acknowledged that the Spanish shot-stopper has not been brilliant in recent games but hoped the former Atletico Madrid man would use the performance as a springboard to further successes.
“I don't know if any other goalkeeper in the country would have saved that shot from Mata,” the Scot told reporters on Friday.
“His speed and agility is outstanding. David knows he had a bad day against Liverpool in the cup. But goalkeepers can have those days.
“Last week's performance will help. He saved us a point.
“When you get a free-kick with the last kick of the game and your goalkeeper makes a save like that, you have to say it's a point saved.”