Manchester United were beaten 3-1 by Brighton at Old Trafford as the home crowd turned on manager Erik ten Hag.
Ten Hag has enjoyed the overwhelming backing of United fans since his arrival last summer and the majority have supported the Dutchman in his current dispute with winger Jadon Sancho.
But they let Ten Hag know they did not agree with his decision to replace new signing Rasmus Hojlund with Anthony Martial 19 minutes into the second period in no uncertain manner, as a cacophony of boos rang round the stadium before the Dane was applauded off.