Onana has had a campaign to forget, with plenty of individual errors leading to goals in both the Premier League and Europa League leading many to believe that United will try to cash in on the 29-year-old this summer. The shot stopper was described as "one of the worst keepers" in the club's history by the former United midfielder Nemanja Matic and has not helped his reputation since that statement.
Van der Gaag thinks the pressure the Cameroonian international is under is heavily affecting his performances and that playing for United can cause any player to act up no matter their ability due to expectations from fans.
"We cannot forget the impact Man Utd has on everyone," he said. "That criticism is there, excellence is expected and players have to deal with that. The other part is that there will always be comparisons.
"He is under pressure and scrutiny but he has overcome many challenges in his career before. At the start of last season, everyone was saying he was United's best and most consistent player so it can change quickly."
The Athletic reports that on the back of this season, Onana could leave Old Trafford this summer as manager Ruben Amorim has likely grown tired of his inconsistent performances. Amorim will have a busy few months ahead of him as he searches for a striker and a goalkeeper that he hopes will boost United into a European spot next season.