United slipped out of the top four on Sunday following a dismal 2-0 defeat at Newcastle United, who moved into third place as a result.
Both clubs, along with fourth place Tottenham, are tied on 50 points as the battle for Champions League qualification intensifies.
Ten Hag’s side have not win a Premier League game since February, maintaining their form in the FA Cup and Europa League in that time but failing to consolidate their place in the top four.
A win on Wednesday night against Brentford will send them third again but ten Hag has warned his squad have failed to meet his expectations in recent weeks – warning those who do not step up that their places at the club will be under threat in the summer.
‘Of course you have to match certain standards,’ ten Hag said.
‘You have to match certain standards and I know in a season you don’t only go up one way, you will have fluctuations. But you have to know why you are where you are and what brings us into that position.
‘Sunday was about determination, passion and desire – and I missed that. When they can’t get it, then they’re in the wrong place.
‘When you have a strong opponent who play above their level – and many teams do against Manchester United – then you get killed. And we did on Sunday.’
United’s cause has not been helped by the absence of Casemiro, will sit out against Brentford and against Everton on Saturday in the final games of his four-match suspension.
Christian Eriksen’s absence has also been felt with the Dane sidelined in January with an ankle injury but the midfielder is now closing in on a return although the visit of Thomas Frank’s side will come too soon.
‘Not for (Wednesday) but he’s returning on the pitch,’ ten Hag said.
‘He’s returning into team training (on Tuesday), so we have to see how quick he can now make the progress.’
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