The Dons even missed a penalty when it was still goalless - Harry Pell seeing his effort saved by Pompey goalkeeper Trevor Carson.
It was Mohamed's second debut for the club, having this week signed on loan from Port Vale until January, and Bassey believes he will continue to be a match-winner for the Dons.
"We're expecting exactly what he gave us for an hour. He carries a threat. He runs in behind, he's powerful and he works for the team. He's a good lad," said Bassey.
"He gave us everything he had but he's run out of legs a little bit. He hasn't played a lot of football this year but he'll get better with game. I thought for an hour he was first-class.
"They players are a lively bunch and they enjoy winning, which is always good. We're respectful of the opposition but we have to celebrate our wins as they're hard-fought, including this one.
"But the boys will enjoy it and they'll have a couple of days away from the training ground now and come back to work next week to prepare for Bury.
"In the first half we played well but in the second half we lost our way a little bit. When you're losing it's easier in a way as you can go for games."
Meanwhile, Guy Whittingham, who last week celebrated a year in charge of Portsmouth, admitted the defeat - a third in a row for Pompey - was a difficult one to swallow.
"It's a defeat that really makes you think deep about how you put things right," he said.
"We'd been going very well up until last week and within a week we've lost three games.
"You have to think back to going back to basics. We've conceded far too many goals the past two games through basic defensive errors - and I'm not just talking about defenders I'm talking about as a whole team. That has to be put right.
"When emotions are running through everybody you can shout all you want but you have to try and talk sense. It's a result that's very hurtful.
"It's not a case of protecting players, we're all in this together and we weren't good enough. We all have to put that right.
"You go into their changing room and you hear their changing room buoyant and celebrating and we sat and listened to it. I made everybody hear it because it's not a nice thing to hear and it shouldn't be."