The Tayside club have recorded back-to-back wins in recent weeks over St Mirren and Kilmarnock to end a seven-game winless streak which began over the festive period.
McNamara's side are sitting fourth in the table and beginning to recapture the kind of form which earned them no shortage of praise prior to Christmas.
He said: "The lads are looking forward to the match.
"Motherwell are a good side and it's one which we should be going into with a bit of confidence.
"We've had a couple of positive results in our last two games which have been well deserved. We still haven't been at our best which is a good thing in a way.
"We know we can play better but the important thing is that we're back into the winning habit.
"Winning matches breeds confidence and we will need to be brave on the night against a quality side like Motherwell."
McNamara is full of praise for opposite number McCall for the rebuilding job he carried out at the Lanarkshire club over the summer.
However, he maintains the Taysiders will focus first and foremost on their own strengths as they attempt to further climb the table.
McNamara said: "Stuart has done a great job at Motherwell again this season. He did lose some very good players but has replaced them and they're still getting results.
"However, it's about what we do in the match. That's always our approach and that's something which will never change.
"We need to show the same kind of energy and enthusiasm levels we showed last weekend to beat Kilmarnock. If we manage to do that, then hopefully we can cause Motherwell problems on the night.
"We didn't all of a sudden become a poor side when we went through that difficult run of games.
"We have got belief in the players and hopefully this game will bring out the best in them.
"It's live on television and the supporters should relish it. They have a part to play and we hope to give them the sort of result they're looking for."
United could hand a return to defender Gavin Gunning, who is back in training after a recent knee injury. Teenager Ryan Gauld is fighting to shake off a niggling hip injury in time to face Well.
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- Stuart McCall