Manchester United staff already have concerns about finishing in the top four this season, a source has told ESPN, after Manchester City inflicted a fifth Premier League defeat of the season.
City's 3-0 win at Old Trafford on Sunday left United eighth in the table, 11 points behind leaders Tottenham and eight points adrift of the Champions League places.
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It has prompted fears within the club that they are facing another season out of Europe's top club competition after failing to qualify four times in the last 10 years.
Sources have told ESPN that United still have faith that manager Erik ten Hag can turn things around, although there is an acceptance that form will need to improve drastically if they are to finish in the top four this season.
United play Newcastle in the Carabao Cup on Wednesday before back-to-back away games against Fulham and FC Copenhagen. Their last game before the November international break is against Luton Town at Old Trafford.
A source has told ESPN that United are hopeful of having Aaron Wan-Bissaka available before the break after missing the last nine games with a hamstring injury while Casemiro, who missed the Manchester derby with an ankle problem, is also close to a return.
United's list of absentees has numbered 16 first-team players at times this season and, according to a source, club chiefs believe it is an unfortunate factor which has seriously impacted the start to the season.
However, there are concerns within the dressing room that the intensity of the training sessions set up by Ten Hag and his staff are contributing to fatigue and, in some cases, injuries.
Some senior players have already played more than 20 games for club and country, including a long preseason schedule which included eight matches, and there is a feeling that more time could be dedicated to recovery to better prepare the squad for match days.