After a vicious clash of heads between Dundalk striker Pat Hoban and Derry City's Ryan McBride, the latter was taken to hospital
Collins criticised Pat Hoban for the nature of the challenge which led to McBride's injury, suggesting that he intentionally set out to hurt the defender, and said that the referee, Tomas Connolly "bottled it" by not giving the 22-year-old a red card.
"He's done him. I believe he's done him," Collins told radio station Drive 105 after the game.
"I think the referee's bottled it, for sure. At the end of the day, win, lose or draw, someone coming in and doing someone like that, for me, it's not on. It's cowardly."
Goals from Brian Gartland, Richie Towell and David McMillan condemned Derry to a 3-0 defeat against Stephen Kenny's charges and Collins said that he it was difficult for his team to compete with last year's league runners-up.
"It was what we expected coming into the game," admitted the Candystripes boss.
"People have to get real. [Dundalk] are the best team in the league at the minute, there's no doubt in my mind about that, they've proved that in their previous fixtures and coming here we tried to keep it as tight as we could.
"We matched them man for man, we frustrated. It was brutal to watch, I mean, we knew that. If you tried [to get the ball down and pass] and open the game up, they'd torture you."
The result sees Dundalk move into third place in the Premier Division, level on 13 points with Shamrock Rovers, while Derry are eighth with six points ahead of their game against Athlone Town on Friday.