The Dutchman was sacked by Manchester United in May last year, just days after winning the FA Cup.
Van Gaal came in for plenty of criticism during his time in charge of the Reds Devils – partially for his style of play that saw them score just 48 league goals as they finished fifth in the 2015/16 Premier League table.
But Wayne Rooney reckons the former Barcelona boss would have eventually got it right if the fans showed more faith in him.
“He (Van Gaal) got a lot of stick. I believe if he stayed it would have got better,” Rooney told talkSPORT.
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“He looked at all the small details not only off the pitch but on the pitch.
“I think the one thing he did was keep the standards with the players, he was demanding the best from you every day.
“We used to film the training sessions, sit back and watch the training sessions back.
“It was tough for the players in that aspect but if he stayed we would have got better.”
Jose Mourinho succeeded Van Gaal and took United to Europa League and EFL Cup glory in his first season in charge.
United finished a disappointing sixth in the league but Everton ace Rooney believes his former side are in good hands with Mourinho in charge.
Rooney added: ”Jose came in and last season in the league we struggled and weren’t consistent enough.
“Obviously in the cups United did well. I could see where Jose was going with the team and they will be a big success.”