Ex-Liverpool defender Jamie Carragher made headlines this week when he seemed to suggest Rashford may have to leave Old Trafford in order to fulfil his potential because he is unlikely to displace Romelu Lukaku as the team's starting centre forward.
Carragher received a lot of support for that opinion, with others now piling on.
However, Mourinho has accused his critics of 'compulsive lies' over Rashford insisting that the 20-year-old, who scored twice for England during the international break, has played regularly for United.
Mourinho noted that Rashford has actually featured in more games than any United player in each of the last two seasons, before joking that he is expecting to be criticised for leaving a suspended Rashford out of the United team that is due to face Watford on Saturday evening.
In a lengthy retort at his weekly press conference, Mourinho defended himself to the hilt, even comparing Rashford's playing time to the similarly aged but much less used Dominic Solanke at Liverpool, Dominic Calvert-Lewin at Everton and Ruben Loftus-Cheek at Chelsea.
"Speaking about Marcus, I think I can expect that on Sunday I'm going to be highly criticised for not playing him [on Saturday] because some of the [media] are really obsessed with me and some of them, I think, have a problem with some compulsive lies," the boss stated, via ManUtd.com.
"In the 2016/17 season, Marcus Rashford played 32 Premier League matches, 11 Europa League matches, including the final, three FA Cup matches, six League Cup matches, including the final, and the Community Shield," he explained.
"He had 53 appearances, but if you want to take minutes played, he played 3,068 minutes and, if you want to divide that into 90 minutes of matches, he played 34.2 matches of 90 minutes in 2016/17.
"In 2017/18, he played 35 matches in the Premier League, eight in the Champions League, five in the FA Cup, including the final, three League Cup matches and the UEFA Super Cup. He played a total of 52 matches with 2,676 minutes. If you divide that into 90 minutes, it gives 29.7 matches.
"With me in two seasons, he had 105 appearances, 5,744 minutes, 63.7 matches of 90 minutes, including five finals."
Mourinho went on to describe Rashford as a 'good kid' and a 'good player' who is fully aware of the support that the club have given him and continue to give him by giving him a new contract (not yet announced) and the famous number 10 shirt.
"Since I've been here, Marcus Rashford has been selected for every single match - he was never out of selection because of my decision or because he was injured or, like in this case, because he is suspended. He was never, never out of selection, so he knows and that's the most important thing.
"But again, media is very important and I think it's important the Manchester United supporters know the truth. That's why I'm going so specific about these numbers."
Rashford, whose suspension for United's next three domestic games is the result of the red card he received against Burnley in his last outing before the international break, is reported to be determined to stay at United and fight for his place.