Roy Keane slammed Trent Alexander-Arnold's defensive efforts in Liverpool's 2-2 draw against Manchester United on Sunday.
United took a 1-0 lead in the 52nd minute Anfield after Lisandro MartÃnez breezed past Alexander-Arnold to fire a shot past Liverpool goalkeeper Alisson.
Before the goal, United legend Keane had fired a warning shot to the right-back -- who has been linked with a move to Real Madrid this summer -- at halftime.
"We talk about how brilliant Trent is going forward, but Trent's defending today, my goodness, it's like schoolboy stuff," Keane said on Sky Sports.
"They talk about him going to Real Madrid, the way he's defending, he's going to Tranmere Rovers after this, he's got to do better."
Liverpool equalised at Anfield through Cody Gakpo, before taking the lead thanks to a penalty from Mohamed Salah.
However, Amad drew United level in the 80th minute as the sides had to settle for a point each.
Alexander-Arnold was replaced by Conor Bradley in the 86th minute.
A source told ESPN last month that Liverpool had rejected an offer from Madrid to sign Alexander-Arnold in the January transfer window.
The 26-year-old's contract runs out in June, with teammates Salah and Virgil van Dijk also out of contract in the summer.
