The defender has sealed a one-and-a-half year deal, with a club option for a further year, after making a promising impact as he’s progressed through the Blues ranks.
Mnoga is now fully fit after recovering from the metatarsal foot injury picked up in a freak accident at Victorious Festival in August.
And Pompey have been quick to secure the 17-year-old’s future after making three senior appearances to date.
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Now Jackett wants to see the former Trafalgar School pupil break into his senior plans moving forward.
He said: ‘It’s really good news for Haji, if a bit delayed because of his injury.
‘I’m pleased. He’s half-way through his second year but had a number of first-team games in the Trophy last season.
‘He had a good pre-season so I’m pleased to get him back.
‘I’m pleased to get him back. He’s had three youth games, a number of training sessions and has been training with the first team of late. He’ll continue to do so.
‘He has to try to establish himself and train with us on a full-time basis..
‘Why can’t he push into the team now? That’s where he has to look. That’s his challenge.
‘I think it is (realistic). How long it will take him I don’t know.
‘He’s 17, but he’s showed enough promise and he has to do well enough to get into the side this season or next.’