The 20-year-old midfielder broke into the first team last season and made a big impression in his breakthrough campaign at Newcastle.
But he was injured at the start of the ongoing campaign and has played just five times in the Premier League so far this term.
Longstaff has not played since the 3-0 defeat at Arsenal and has not made the Newcastle matchday squad in the last three league games.
Bruce insisted that despite his absence from the team at the moment, the midfielder still has a big future ahead of him at Newcastle.
He urged Longstaff to get through the current period as he is certain that the starlet’s time will come at some point.
The Newcastle manager said in a press conference: “He’s not in the side, but let’s not forget he’s got a huge future – there’s no question about that
“He had a big rise last year and finds himself not in the team at the moment so he’s just got to stick with it.
“His time will come again, that’s for sure.”
Longstaff will enter the final year of his contract at Newcastle in the summer.
