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 Leeds United loanee once again struggled in London.
Sheyi Ojo of Ibrox side Glasgow Rangers made headlines for comments about Celtic.
The Gunners defender has been struggling with injury but is back in training for Unai Emery and co.
Loris Karius is on loan at Besiktas from Liverpool.
Marcelo Bielsa’s Leeds United have lost against Millwall in the Championship this afternoon.
The Leeds United youngster was handed a six-week suspension in early September.
Ryan Jack hobbled off during Rangers' match in the Europa League last night.
Arsenal ace Mesut Ozil was not included in the squad to face Standard Liege.
Leeds United forward Tyler Roberts was substituted on and off in midweek.
Arsenal youngster Ainsley Maitland-Niles failed to impress supporters with his performance last night.