Danny Cowley felt Pompey were just missing a spark to turn one point into three at AFC Wimbledon.
The visitors recovered from a slow start to dominate the League One contest and created several good opportunities.
Mahlon Romeo rattled the crossbar with a thunderous strike, while Nik Tazanev denied Tyler Walker, Ronan Curtis and Sean Raggett.
And Cowley was disappointed that his side could not find that all-important breakthrough at Plough Lane.
The Blues boss said: “It was a competitive League One game, although I wasn’t happy with our way into it.
“But I thought that we started to wrestle control from about the 30-minute mark and had a positive end to the half.
"I thought we had good momentum and it felt like we were going to go on and win – we certainly did enough."
“Then we came out after the break and had really good control and dominance, but couldn’t find a goal.
“It was the story of our recent performances because we got into the final third an awful lot and needed a little bit of quality with our final action.
“I’ve looked back and there should have been a clear penalty, while their goalie has made some key saves and we’ve hit the bar.
“I thought we had good momentum and it felt like we were going to go on and win – we certainly did enough.
“You need that little moment of quality to get on the right side of tight games, but I feel our fortune will improve.”
Walker was handed his debut alongside George Hirst up front and Cowley was pleased to get his man.
He said: “It’s brilliant to bring Tyler into the club and we didn’t think it would be possible, but we got the opportunity and we’re delighted he’s here.”