United entered the new year in eighth place in a congested SPL table - Peter Houston's men are nine points off second place in the standings - after a 10-match winless run at home and a current four-match streak without a victory.
Hegarty believes victory at Pittodrie against Aberdeen could provide the required boost to turn the tide in United's favour.
"It would be great to get a result with the winter break coming up; to go in with a victory," said Hegarty, who spent 16 years at United as a player and enjoyed some memorable encounters with the Dons. "When you start the season again you've got a bit more confidence.
"We've got to make sure we do well and hopefully get a result."
Houston and first-team coach Gary Kirk watched Aberdeen beat Dundee 3-1 last Saturday with a hat-trick from in-form Niall McGinn and United are aware of the challenge that awaits at Pittodrie.
"We've got a game on our hands, but hopefully we can appease our fans," Hegarty said. "These games are always important because you have bragging rights in the north east.
"These games probably define your season. We've got to try to get back to winning ways and if we can do that we'll be delighted."
The straight red card shown to defender Brian McLean against St Mirren means United will be forced into a defensive reshuffle.
Unless Sean Dillon recovers sooner than expected from a thigh injury, captain Jon Daly is likely to drop back from striker to centre-back, while midfielder Willo Flood (groin) is doubtful after going off midway through the first half of the 4-3 loss to the Buddies.
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