Mourinho has advised Martial to follow the example of United team-mate Marcus Rashford.
Mourinho has advised Martial to follow the example of United team-mate Marcus Rashford, who battled back from a run of inconsistent performances to score a crucial goal in last weekend's 2-0 victory against the Premier League leaders.
The United manager, preparing for the second leg of the Europa League tie with Anderlecht, also admits he is uncertain what role Wayne Rooney will play as he struggles to overcome injuries.
But the status of Martial is of particular interest, as United must pay his former club Monaco a further £8.5 million ($10.8 million, 10 million euros) the next time the France international scores a goal for United.
Martial, 21, cost United £35 million in 2015, with the fee to rise to a potential £56 million based on incentive clauses.
The latest kicks in when he scores his 25th goal for the club, a mark of which he is currently one short.
But, despite flashes of brilliance, Martial has yet to hit consistent form and Mourinho is clearly losing patience, leaving him out of his squad altogether on Sunday.
"I know we are together for almost 10 months now. The same way I know the players much better now and the players should know me also much better now," Mourinho told reporters on Wednesday.
"That's why Marcus Rashford, even without being since September with a goal in the Premier League, even without that, he was always a player that I trust, always a player that I play, always a player that I support.
"Because he was always coming in my direction, in the direction I want from a player, what I want as a Manchester United player.
"He's about that. It's about getting to know each other better and better and better and going in the direction of things we like.
"Do I think Anthony is a player with great potential? Yes I think. Do I think he can play successfully for me? Yes I think. But he needs to give me things that I like very much."
Rooney, 31, was also absent from the Chelsea game, with an ankle injury that adds to a list of problems that has featured knee and muscular woes and illness since he became United's record goalscorer in mid-January.
England striker Rooney has played just 131 minutes of league football since then and has not been involved in the Europa League since December, casting doubt on whether he will play for the club again.
"He is working now and he is improving and, if in this training session the answer is positive, I will select him to be on the bench tomorrow (Thursday)," Mourinho said.
"With his experience and know-how of this knock-out phase, he is a player who can be useful.
"If we need a goal, he can help us. If we need to keep a result, have possession, keep the ball, he can help us too.
"So hopefully his answer in the training session is positive.
"He had not big problems during the season, but a few small problems and sometimes when you get into a certain age – I am not saying he is old, we have older players, there are many older players in great condition – but when you get to a certain age, it is a little bit more difficult to recover. I think it is just that.
"We lost players in the January market, we didn't bring in anyone, we lost players in international week, so we need everyone that can and Wayne can. Hopefully he is there."