Danny Cowley admitted Portsmouth face an uphill battle to make the Sky Bet League One play-offs after losing 3-1 at relegation-haunted Swindon.
Former Pompey captain Brett Pitman came back to haunt his old club by scoring twice as Swindon kept alive their faint hopes of staying up.
Pompey head coach Cowley said: “My overriding emotion is obviously disappointment; we didn’t do well enough in the decisive moments in the game at both ends.
“I thought we had clear control and dominance between the boxes, for us to concede three goals with that much control – more than 75 per cent possession – and them having only 11 touches in our box, that’s pretty painful.
“Also, offensively we got into the final third on numerous occasions, with some really good play, but lacked the final action.
“If you don’t do well in the key areas of the pitch then you don’t win games – and that’s the reality.
“It’s a great job and a brilliant club but it’s also a huge challenge, there’s no hiding place from that. We haven’t done well enough in the last four games.”
Pitman netted a goal in each half before Tyler Smith sealed the points for the struggling Robins.
Jack Payne teed up veteran striker Pitman to lash into the net to open the scoring in the 18th minute.
Former Bournemouth star Pitman doubled Swindon’s lead from the penalty spot in the 61st minute after Charlie Daniels had fouled Smith.
Pompey gave themselves hope eight minutes from time when Curtis brought down a John Marquis pass and fired home.
Curtis and Andy Cannon both came close to plundering a late equaliser as the visitors cranked up the pressure.
But Swindon wrapped things up the points to boost their survival hopes in stoppage time courtesy of Smith’s well-taken finish.
The win leaves the Wiltshire team seven points adrift of survival with only three games to play.
Swindon caretaker-manager Tommy Wright said: “It was a good performance from us tonight and I felt we were thoroughly deserving of our win against a side with promotion ambitions.
“I wanted a response from our players and they gave me one. I just wish I knew where that performance had been these last few weeks and why they were not able to do that three or four games ago.
“I want to bring a bit of pride back to the club in the remaining games and we will keep fighting to the end.”