Sammy Braybrooke and Amani Richards found the net in the north-east on Friday evening but four goals from the hosts sent Sunderland on their way to three points in Premier League 2.
Harrison Jones opened the scoring after just three minute at Eppleton Colliery Welfare Ground, before the recently returned Braybrooke levelled things up again in the seventh minute. First team attacker Bradley Dack put the hosts back in front, ensuring the lead at the interval.
Jones scored his second goal of the game little over the hour mark to give the Black Cats some breathing space, but Leicester made life difficult by reducing the deficit in the last fifteen minutes; Richards scoring the goal.
But as City pushed to salvage a point, Sunderland netted a fourth through Joseph Ryder to keep all three staying on Tyne and Wear, as the young Foxes now look towards a PL2 test against Manchester City at LCFC Training Ground on Monday 8 April (7pm BST kick-off).
The details...
City: Young; Cover, Grist, Amartey, Wormleighton (c); Braybrooke (Raikhy 65'), Joseph (Briggs 65'), Cartwright; Thomas, Otchere (Richards 63'), Marçal.
Unused subs: Doherty, Lindsay.
Goals: Braybrooke 7', Richards 74'.