After an impressive start to the Conference Premier campaign, the Lambs hit the buffers in October with seven straight league and cup defeats.
And although Tamworth returned to winning ways with back-to-back wins over Chester and Ebbsfleet in November, MacKenzie believes it was the 2-0 FA Trophy victory over Mansfield which has breathed fresh life in the Lambs.
"It was one of our best performances away from home," said MacKenzie, who had two spells at Field Mill, playing 71 times for Mansfield from 2002/04.
"To be honest it was the game that kick started us again.
"It gave us a bit of belief and since then we have gone from strength to strength really."
MacKenzie, who returned from a heel injury as a substitute in the 0-0 draw at Wrexham on Tuesday night, says the Lambs will go into Saturday's home game full of confidence.
And he believes that high-flying Mansfield will not be relishing a trip to The Lamb.
He said: "We have already beaten them once this season which was very good.
"We have a great record against sides in the top half of the table as well.
"So they should fear us more than we fear them – coming here will not be easy for them."
A win over Mansfield could see Tamworth move into the top ten in the league but MacKenzie admits a play-off bid is probably beyond them.
"Realistically we would have to go on an incredible run now to get in the play-offs," he added.
"We are still 13 points or so away.
"Of course, we haven't written it off yet though.
"It's a massive ask but our aim is simply to see how many games we can go on unbeaten in the league.
"And, of course, we still have the FA Trophy to look forward to as well.
"We have Salisbury next and if we get through we are in the last four.
"Once you are in the semi-final, it's a lottery and whoever performs over two legs will go through to a Wembley final which would be fantastic."