Haji Mnoga has joined Gillingham on loan for the remainder of the 2022/23 campaign.
The 20-year-old Tanzania international defender was part of the Pompey side that won 2-1 in a friendly at Priestfield Stadium back in July.
Blues boss Danny Cowley said: “It’s a brilliant loan for Haji. He’s been focused, determined and has trained fantastically well every day to make real progress.
“Neil Harris really liked him when we went to play Gillingham in pre-season and then came to watch him at Crawley on Tuesday.
“It gives Haji the opportunity to play on the right of a back three, which is the formation they’ve been using. That’s a really good fit for him at this stage of his career.
"It’s a brilliant loan for Haji. He’s been focused, determined and has trained fantastically well every day to make real progress."
“We’re really excited to see how the loan progresses and we feel it can be a positive move for both parties.
“Haji is a shining example of the great work done by our academy and I know how much work has gone into his development for many years.
“He’s got a great future in the game and I look forward to watching this next stage of a promising career.”
Mnoga – who spent time with Bromley and Weymouth last term – has featured 18 times for the Blues since progressing through the academy, including three cup appearances this season.
He previously represented England at youth level before making his senior debut for Tanzania earlier this year.
Gillingham were relegated from League One at the end of the last campaign and face Swindon on home soil on Saturday.