Darren Powell accused Hampton & Richmond Borough’s players of letting themselves and the club down on Tuesday night.
However, he has also backed them to sort out the start of their season this weekend.
The Beavers were woeful against Wingate & Finchley, going down 4-1 in front of their own supporters, having suffered late 1-0 agony on the opening day of the Ryman Premier season at title favourites Margate.
Joint manager Powell said the performance was “totally unacceptable” and would not allow a repeat display this weekend.
Witham, last season’s play-off winners from Ryman Division One North, visit the Beveree and the former Brentford defender is expecting a reaction.
He said: “Let’s be clear with this, Tuesday night was so poor – they let themselves down and more importantly they let their club and its supporters down.
“You can’t put in such a bad performance in your first home game of the season, it sets the wrong tone.
“After leaving Margate unlucky to lose, we let a team that got reprieved from relegation last year take the mickey out of us.
“The result was a fair one and that hurts.”
He added: “It’s down to them to respond now, and it’s down to myself and Paul (Barry) to get a reaction.
“We need to show the supporters we’ve got something in us, that there is something to look forward to this season.
“We’re good enough, we have certainly not lost the faith in the team, but we have got to show it now.
“We have to make a statement.”