Sky Blues boss Mark Robins believes that missed chances cost his side at least getting a point at Fratton Park.
City had led at half time through a Jordy Hiwula strike, but goals from Tom Naylor and Brett Pitman secured the three points for Pompey.
Robins was left frustrated that his side left Hampshire with nothing to show for their efforts.
“We’ve created brilliant chances; we’ve scored a great goal.” He said.
“Luke has had two unbelievable chances; they are guilt edged chances and if they go in it is game over and we win three or four nil.
“As it is, they are probably one of the best second half teams in the country and they’ve come back and what they have got in their armoury is different to what we have.
“They have got that power that shone through from the set plays. When you have got a bit more nous which they have, the bench is strong, and you have got to try and cope with that, but we ran out of steam a little bit.
“The front end tried to keep working for the 90 minutes in this heat, it didn’t help yesterday when we had a fire at the hotel, we had no food, so we had to order in from a well-known chicken establishment which wasn’t great.”
Despite the defeat, Robins was proud his sides performance:
“We’ve come and played and that’s been a really good performance today, it’s just disappointing we haven’t come out on top or got anything from the game.
“We’ve got a good team and a good group of players that are almost there.
“We play a really good brand of football, the supporters are behind them, its just that extra bit that we have got to try and get right for next season.
“I thought Kelly was magnificent today in terms of the experience, I thought he was outstanding.
“They (Portsmouth just had those extra couple of players across the pitch that have that extra couple of years under their belts.”
“I think it was a good game, the condition of the pitch was outstanding and the way in which we played on it was pleasing, we have just failed to come out on top and see the job through.
“But there is no way we deserved to get nothing from that game.”