The Red Devils boss revealed that the Spanish goalkeeper was supplanted by Anders Lindegaard for Sunday's victory over Southampton after a notable mistake against the Cottagers
The Spanish shot stopper was replaced by Anders Lindegaard between the sticks as the Red Devils narrowly defeated Nigel Adkins' men 3-2 at St. Mary's Stadium.
And the Scot confirmed after the game that De Gea's spill against the Cottagers, which allowed them to get within a goal of earning a point at Old Trafford, cost the former Atletico Madrid man.
"I think young David made a mistake last week," he told Sky Sports after the win on the south coast. "He knows it. With the form he's been in, he's been making some fantastic saves, but one error like that could have cost us the game.
"It's just a learning process for him and he'll be back in a couple of weeks' time after the international break. Anders had his first game. I thought he was a little bit nervous at points but he's a very good keeper also. I don't think it's a big issue but it's something you have to deal with."
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