The Magpies academy graduate, 19, was in Rafael Benitez's matchday XI for the Premier League finale at Fulham.
The Magpies ran out 3-0 winners over the Elland Road side, with the Whites boss Carlos Corberan fielding a strong side.
The Magpies Under-23s defender played alongside Longstaff earlier in the season, the latter going on to impress for the first team.
The Real Betis ace is a reported transfer target for Liverpool.
Tottenham Hotspur boss Mauricio Pochettino has been pushing for signings this summer.
Tottenham Hotspur boss Mauricio Pochettino is said to be keen on Bruno Fernandes.
Aston Villa will be hoping to secure the signature of the ever-popular figure Tyrone Mings this summer as they prepare for Premier League football.
Leeds United will be hoping to go one better next season and earn promotion to the Premier League.
Ibrox club Glasgow Rangers defender James Tavernier is reportedly on the radar of Aston Villa and West Bromwich Albion.
Leeds United have sold Paudie O'Connor to Bradford City.
Tammy Abraham, Tyrone Mings and Kortney Hause were three huge loan successes for Aston Villa last season.
Tottenham Hotspur pulled out of the race to sign Andre Gomes, and Everton have snapped him up for a bargain fee.
Aston Villa and Leeds United fans react to Garry Monk being sacked by Birmingham City.