The 70-year-old praised De Gea - who has not played a Premier League game since conceding twice against Fulham in the second match of the campaign - following United's midweek win away to Cluj in the Champions League after a string of late saves preserved a 2-1 win.
Anders Lindegaard, 28, started the last four league matches in his place for Sir Alex, but it is unclear whether the Danish stopper will remain in goal for Sunday's trip to Newcastle.
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"I don't know whether I should play him on Sunday or not but the way we have been doing it in the last few weeks has worked quite well for us.
"Everybody wants to play, goalkeepers are no different, but the way I look at it at the moment is getting the two of them experience will help me in the long term."
The Old Trafford boss says he is not too concerned at the lack of a genuine No.1 as he feels both players have plenty of time left to establish themselves.
He said: "Peter Schmeichel was 27 when he joined us. Everyone was talking about a young goalkeeper joining us but he was 27, and he gave us eight great years.
"Goalkeepers can play until their late 30s quite easily, look at Brad Friedel for instance, and Peter Shilton played in the 1990 World Cup and I think he was 40.
"Goalkeepers can last longer. If they look after themselves even better, but as long as they keep their agility and their speed they can play to a good age."