After an indifferent pre-season campaign that was cut short due to the birth of his second-child, Martial received a fine for not returning back to the training camp on time and has since been at loggerheads with Mourinho.
According to British publication Starsport, Mourinho asked vice-executive chairman Ed Woodward to sanction a transfer for the France international in order to find a left-winger more suitable for his tactical set-up.
However, Woodward has reportedly rejected the notion, claiming the Martial, who joined the club for a reported £57.6m in 2015 is good enough to succeed and not be sold at a cut-price.
The report further suggested that Martial's start in the 3-2 defeat against Brighton was sending a message to Woodward, after an uninspiring hour at the Amex before being hauled off.
Former United favourite Lee Sharp believes his run-ins with the current squad, which included public fallouts with club-record signing Paul Pogba, will see him face the sack before Christmas.
"Mourinho is the wrong man for the job. When he came to Chelsea the first time he was quite charming and fun, but now he just seems dour and fed up," Sharp told Sky Sports.
"He's moaned about not signing new players and not bigging up the ones he’s got. The football’s not entertaining and what makes it twice as bad is that their two biggest rivals, Manchester City and Liverpool, do play exciting football.
"His negative style does not fit in with the expansive football that United fans want. I think he’ll be gone before Christmas."