Whitestone awarded two penalties to the managerless Sky Blues, both of which were converted by Marlon King, with the second spot-kick being awarded for a handball which led to a red card for Hayden Mullins. Gary McSheffrey scored in between King's goals as Coventry eased to three points which put to bed any lingering fears of relegation, but Cotterill, whose side's hopes of making the play-offs have all-but gone, was fuming after the game.
"There was no way we should have lost that game 3-0. But there was one obstacle we couldn't overcome, and it wasn't Coventry City," he said.
"It's very difficult. It's bad enough when you don't get one or two decisions, but when they come as thick and fast as that, it's very, very difficult for players not to get frustrated."
"(The Mullins incident) was not a penalty. It hit Hayden Mullins absolutely square on the thigh. It was belted at him, it hit him on the thigh and then it hit him on the hand. There is no way that is a penalty and a sending off.
He added: "Unfortunately it will say in the papers Portsmouth 0 Coventry 3 and that's all anyone will be interested in. I would be absolutely delighted and rubbing my hands if I was Andy Thorn on the way home. He will be loving it because he knows 3-0 flatters them."