The Bannsiders failed to make it three Sports Direct Premiership victories in a row as Noah Stewart's brace and Alexander Gawne's thunderbolt earned the Sky Blues their first home victory of the season.
Coleraine would have to play an hour of the contest with 10 men following Matthew Shevlin's dismissal after the striker was adjudged to have used a high foot when challenging for a loose ball with United stopper Sean O'Neill.
Kearney’s men did half the deficit through Josh Carson’s penalty kick on 64 minutes but the Coleraine chief remarked the damage had been done by poor defending for Stewart’s two early second-half goals.
"We haven't helped ourselves as we had an in-depth discussion at half-time about how we manage the first 15 or 20 minutes of the game after the restart," he said.
"For us, I firmly believed that we could still go and win the game as we have enough quality to score a goal in the second-half.
"But what I also said to the players is that we've got to pick and choose our moments of when we go and down that, but most importantly, we've got to keep the back door shut.
"Ballymena haven't had to earn their first two goals and that's the frustrating part and with the form they're in at the minute, if we had got to 65 or 70 minutes at 0-0, the momentum could have swung and things become edgy.”
Kearney conceded he doesn’t know how many games star striker Shevlin will be suspended for as his team face Cliftonville and Crusaders in their next two games, as well as a meeting against Ballymena United once again in the BetMcLean Cup.
"The fourth official has told me he's been caught in the face, there's no chance he's caught him in the face, it's probably bicep or chest area where the contact has happened,” he added.
"I don't how long it will be for or what the challenge will be deemed as.
"That's the absolute frustrating aspect of it as it's just on today's fixture but possibly the next two or three."