Marcus Rashford’s physical and metaphorical growth is a source of huge optimism for Jose Mourinho after the Manchester United striker’s double helped sink LA Galaxy 5-2.

While big-money signing Romelu Lukaku made his United debut, it was Old Trafford youth product Rashford who stole the show with two goals.

And his notably increased muscle mass also caught the eye, with the 19-year-old evidently growing in more ways than one.

Mourinho told the club’s official website: ‘It’s just the natural evolution of the kid. An accumulation of minutes on the pitch.

‘You change your body when you’re a young kid, he’s already taller than when I arrived 13 months ago. He’s three centimetres taller and he put some muscle on, but without any kind of specific work because his speed is the most important quality.

‘Today he was in a different team to Lukaku [first half and second half]. We will also try both in the same team, which I think can also work.’

Rashford was increasingly called upon during United’s run-in last season as they juggled domestic and Europa League commitments, with the England international – who scored 11 goals in all competitions – selected in the starting line-up for the 2-0 final win over Ajax.

‘Last season in this period everyone was saying it would be difficult for me to play him, but he was one of the top appearance-makers of the team last season, which is good for his evolution,’ added Mourinho.

‘He played in the Europa League, important matches, and he’s learning a lot. He’s a great pro, has a great attitude and last season he maybe was not scoring a lot of goals and missing some chances, but it was not a drama because that’s part of the evolution.

‘We know he is going to score more goals than last season.’