The central defender moved to Parkhead on loan from Manchester City last week to provide another option in the backline, challenging Cameron Carter-Vickers, Auston Trusty and Liam Scales.
He has already featured in Pep Guardiola's first team and so has decent pedigree.
However, he wasn't taking part in full training with the English giants and so will take time to get up to speed, not included in the squad for last weekend's win over St Mirren.
Manager Brendan Rodgers told Sky Sports: “He’s a little bit away in fairness to Jahmai.
“He’s been training with the small group at Manchester City and isn’t quite up to speed yet.
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“You can see his quality straightaway and it’s just going to take a bit of time in terms of his fitness and the intensity.”
When the 19-year-old does get up and running, Rodgers expects him to offer a lot.
“He’s a young player but got good experience," he added.
“He’s at Manchester City for a reason. Has good pace, a good defender and impressive in the air.
“We play in a really progressive way and he is a young player who can help with our squad.”