Any optimism provided by a midweek win against Chelsea that had put sixth-placed United only three points behind champions Manchester City in the Premier League evaporated in a 3-0 home loss to Bournemouth.
It was no fluke. Bournemouth dominated the match almost from start to finish and could have won by more than the goals scored by Dominic Solanke, Philip Billing and Marcos Senesi.
United have now lost four times at home in the Premier League this season and 11 in 23 games in all competitions and Ten Hag's future is again under a cloud.
He looked forlorn in the drenching rain and afterwards said his side had not started the match properly.
"I think, as a squad, we are not good enough to be consistent and we have to work as a squad to improve that," he said.
"We are really inconsistent, we have the abilities to do it, but you have to do it every game and every third day.
"As a group, we have to improve. We have to get tougher, so that we are ready for the game, from the start. I said on Friday it can't be in this league if you are not playing on the highest levels because you get killed."
United's fans made their feelings clear at the final whistle as boos rang out and Ten Hag said he sympathised with them.
"I feel sorry for them because they are always behind us," Ten Hag said.
"They expect more from us. And we have to do it from the first whistle."
Captain Bruno Fernandes, who was booked and will miss next week's trip to Liverpool, said the display was not acceptable.
"We did many things wrong today, at all levels, technically and intensity-wise, Bournemouth were much better than us," the Portuguese said.
"We are not consistent enough if you want to be in the top spots. I understand the fans' frustrations."
