The Dutchman is still chasing his first victory as United boss following a defeat and two draws in the club's opening three Premier League outings.
"I'm as disgruntled about our start as everyone else," Schmeichel told The Mirror. "The players lost a lot of confidence and belief in themselves.
"Last season, after winning the championship the year before, they went from one extreme to another. But I know Van Gaal can deliver.
"Time and patience must be given to the team and to him and to his philosophy. He has a plan with everything he does. He has proven himself time and again."
Van Gaal's predecessor, David Moyes, lasted less than a year at Old Trafford as the Scot was sacked for presiding over the club's worst season in the Premier League era.
The Red Devils could mark their first win of the season with the visit of Queens Park Rangers next Sunday.