Jose Mourinho giving Luke Shaw every chance to prove his worth after injury

After shining for Southampton and playing for England at the World Cup, United made the full-back the most expensive teenager in history three years ago.

Shaw has managed just 48 appearances for United since the move due to a mixture of form and fitness issues, most pertinently the double leg break that brought his second season at the club to an abrupt halt.

The 22-year-old returned to the fold last term but Mourinho publicly questioned his attitude, application and football intelligence during a comeback campaign ended in late April by foot ligament damage.

Shaw made his latest return to fitness as a half-time substitute in Wednesday's Carabao Cup win against Burton and, while calling for improvements, the United boss showed restraint when talking about the England international compared to last season.

"He has to work, just that," Mourinho said ahead of Saturday's trip to the left-back's former club Southampton.

"You saw the game, you saw the same as I see, so are you asking if he plays tomorrow? No, he is not playing tomorrow. He has to work. He has to improve.

"Look, he doesn't play for six months. I am not expecting him to arrive on Wednesday and to be man of the match or to be running up and down for 45 minutes.

"It's just a process. He doesn't play for a long, long time.

"You have other players in the Premier League that in this moment who are not starting matches and their managers just say 'they're not in the best conditions'. And we're speaking about some of the best players of the Premier League.

"I heard last week the Chelsea manager saying that, I heard Arsenal manager said that. The players are not in their ideas, in their analysis, they're not in the best form after important injuries and long time without playing.

"Luke had surgery and a long time without playing football. I cannot expect him to be back and to be strong, strong, strong in his work."

Shaw was not alone in finding himself under scrutiny during Mourinho's first season.

Anthony Martial got under the United manager's skin at times, but the forward has returned from the summer with a fresh mentality.

"He's improving a lot," Mourinho said. "Not just on his will, his desire to do it, but being effective on that. Very good. "

Martial's improvements along with the fine form of Romelu Lukaku, Marcus Rashford and the like means Mourinho's faces a challenge shoehorning his attacking talent into the side effectively.

"It's hard for (Martial) but it's hard for many others," Mourinho added.

"So many players are in good moments, good form, playing well. It's hard for all of them.

"When I see the match last Wednesday, the attacking players - Martial, Rashford, (Juan) Mata, (Jesse) Lingard - which one of them deserves to be on the bench tomorrow? No-one.

"Nobody deserves to be on the bench. But they are four, plus Lukaku and (Henrikh) Mkhitaryan is six. I cannot play with the six.

"Yes, sure (Martial, Lukaku and Rashford could play together) - and then I leave Mata and Mkhitaryan out and you say why?"