The Waterside men moved off bottom spot of the table following a well deserved 1-0 win at Dungannon Swifts on Saturday, but Gregg believes this weekend's match with Ballymena United, at Drumahoe, is equally as big.
"Saturday's win at Dungannon although was super only means we have given ourselves a chance of staying away from the bottom two," said Gregg.
"We need to show the same amount of commitment and work rate as we did at Dungannon, when Ballymena visit Drumahoe, because it's the second of or three cup finals.
"Ballymena had a very good win over Coleraine last weekend and I saw Tommy Wright state in a newspaper that his players are playing for their future, so they'll be coming to our place in confident mood and looking for a result."
The Coleraine man will be telling his players at training this week that they can't take their foot off the pedal and feel their job is done after the win at Stangmore Park.
"One swallow doesn't make a summer and I told the players on Saturday to enjoy the trip home and enjoy the win, but that the hard work will start all over again at training this week."
Gregg also feels that the recent appointment of Raymond McGuinness, as his assistant, has helped him both on and off the pitch.
"To be honest whenever I brought in him, it raised a few eyebrows but I feel his two years out of football is Institute's gain, because he has been brilliant.
"He has been a breath of fresh air in the dressing room and the players have responded to him brilliantly."
On the injury front Ruairi McClean is a major doubt with a groin injury, while John O'Loughlin has a slight problem with a bruised elbow.
"Ruairi is really struggling, but I'm confident John will be fine, unfortunately Mark Scoltock will probably miss the rest of the season, however his attitude has been first class.
"Although he has been out for the last nine weeks, he has come to every training session and every match and that's exactly what you want in a player, who is fully commitment not just to the squad, but to Institute FC."