"He has to respond," Neville told reporters. "If he doesn't, it will be a reflection upon him as a character and a personality moving forward.
"The reality of it is Shaw will be given a chance to play in a few weeks' time and it's his performance on the pitch that will count. "
Shaw, who signed from Southampton at the start of the 2014-15 season, was criticised by former manager Louis van Gaal for lacking fitness.
The 21-year-old suffered a broken leg last season and has started only seven league games under Mourinho during the current campaign.
Former England defender Danny Mills backed the Portuguese manager's comments, saying Shaw had no excuse to be unfit.
"Even if he has been injured, there is no excuse not to keep the weight off or to be as fit as you possibly can be and look like you are making the biggest effort ever," Mills told BBC Radio 5 live.
"I think Mourinho has had enough and thinks he can't let this attitude poison any youngsters or drip feed into others.
"Would Sir Alex Ferguson have stood for this? No. Fergie would have just got rid of him."
Several British media reports said Shaw had held talks with Mourinho on Monday and then joined up with the squad ahead of Tuesday's league game against Everton.
(Reporting by Hardik Vyas in Bengaluru; Editing by Peter Rutherford)
Share
