Coleraine edged out neighbours Bertie Peacock Youths in a tense encounter in front of a big crowd at The Showgrounds.
Tommy Rogers's goal at the start of the second half was enough to give the Bannsiders the points and leave it very tight in Group C.
Glentoran's 3-1 win over Global Premier Soccer means the four teams now have three points each with a game to play.
"It's wide open now I think it's split across the board now with everyone on three points," said Coleraine coach John Gregg.
"I said to the players before the game that the door is a little bit open but we have to break it down.
"They were absolutely fantastic as were Bertie's. It wasn't a great game of football, it was nip and tuck, it was nervous, but they sometimes are good games of football.
"I thought both teams were fantastic, it's tough when you're playing in front of a big crowd like that, with so much at stake. One goal won it in the end.
"Big Dan had caused a few problems all day, he's hard to stop when he gets going.
"We managed to break through and it's a fantastic finish from Tommy.
"It was a matter of holding on after that, because we knew Bertie's being the side they are would put us under pressure.
"We had to dig in deep and get the result.
"But the big result for me was there was two teams from the town getting their picture taken together afterwards, and the pleasing thing for me is there is a lot of good players there.
"As much as there has to be a winner and a loser for me the most important thing is the picture afterwards."
Bertie's players were disappointed to drop points after their excellent win over Glentoran in their opener.
Coach Sean Devine felt their exertions on Monday had taken a lot out of his players.
"We have to congratulate Coleraine on their victory, it's a hard one for us to take," he said.
"We had a super performance yesterday, but we probably used a lot of energy, but that's not to make excuses for our defeat.
"We knew the boys were tired last night when they got back. We went to the sea to try and relax our muscles a bit. But we've no excuses today they were the better team.
"We've told the boys that they have to enjoy the rest of the week.
"It comes around fast with another game tomorrow, which is the best thing after a defeat. We will try and put it right against Global Premier Soccer."