Neither Anthony Martial nor Marcus Rashford are happy spending time on the bench, but the competition between them is pushing both to greater heights for Manchester United this season.

With Romelu Lukaku the first-choice number nine and Henrikh Mkhitaryan generally preferred by manager Jose Mourinho on the right flank, Martial and Rashford have had to fight it out for the left-wing slot.

Rashford tends to start, but Martial has proved brilliantly effective as an impact player and after netting the winner against Tottenham Hotspur on Saturday, he said he had no desire to become known as a super sub.

"I want to play," said the France international.

"I don't want to be on the bench, but Rashford played well too, so the manager tried to give us all a chance and we have to score and give assists."

Martial's grievances are backed up by the fact he has been more clinical than Rashford, albeit often having come off the bench to face tiring opposition defences.

With four goals and two assists in 267 minutes of Premier League action, Martial has been decisive roughly once every half of football and has already matched his goal tally from last season.

Rashford has played much more -- 607 minutes -- but his three goals and three assists have come at intervals of 100 minutes.

Underlining the extent to which they have tended to take things in turns, the pair have found the net in the same game only once -- in last month's 4-1 win over Burton Albion in the League Cup.

Prior to Martial's match-winning cameo against Tottenham, Rashford had had the upper hand.

He scored the only goal in United's 1-0 win away to Benfica in the Champions League and netted the consolation goal in their shock 2-1 defeat at Huddersfield Town after replacing Martial at half-time.

- 'Good for the team' -

While both players are popular with United's fans -- Martial due to his excellent debut season in 2015-16, Rashford thanks to his local roots -- there were boos when Martial replaced Rashford against Spurs.

The lack of complimentarity between 21-year-old Martial and Rashford, who turns 20 on Tuesday, is explained to a large degree by the many characteristics they share.

Both are quick, skilful, right-footed players who are honing their trade as wide players in the expectation that they will develop into centre-forwards.

Mourinho drew an interesting distinction between them, however, when he explained his decision to pitch Martial into the fray at Rashford's expense at Old Trafford on Saturday.

"Anthony Martial is the same position as Marcus, but is more comfortable than Marcus dropping in between the lines to help drive the ball and not just attack space," said Mourinho, whose side host Benfica on Tuesday.

One area where the duo differ is in terms of their standing at international level, with Rashford almost a guaranteed starter for England whereas Martial was not called up for France's most recent matches.

But Martial's form, allied to Ousmane Dembele's unavailability through injury and Dimitri Payet's repositioning at number 10 for Marseille, could open the door to a recall when Didier Deschamps names his next squad on Thursday.

A call-up would prove being an impact substitute has not harmed Martial's standing and Rashford, for one, sees no reason why the current set-up should not be sustainable.

"Without it, you don't improve. Young players need that sort of environment around them," he said earlier this season.

"I think we're both enjoying our football at the moment. We're both having our say in the games and it's good for us, good for the manager, good for the team."