The Dutchman has scored just once in his last 12 games for the league leaders, and his winner at Sunderland on Saturday went down as a Titus Bramble own goal, The Sun reports.
According to Ferguson, it may be necessary to monitor Van Persie because the team still does not have complete information on the footballer or the type of seasons that he had had before.
Ferguson further said that Van Persie probably did not have such an intensive season during his stint at Arsenal, adding that the team management will have to examine the issue.
Van Persie, who has scored 23 goals for his club this season, also missed a sitter in United's FA Cup defeat at Chelsea on Monday, the report adds. (ANI )