The 21-year-old midfielder joined on a free transfer from Bournemouth in the summer but has been absent throughout the club's pre-season preparations as well as Saturday's 2-2 friendly draw with Arsenal at Ibrox.
Now Gers manager Steven Gerrard has revealed that the player, who was born in England but has represented Nigeria Under-20s, has been referred to specialists after a routine heart scan detected some possible cause for concern.
Following the collapse of Denmark star Christian Eriksen at Euro 2020, the club are understandably taking no risks.
Gerrard told Rangers TV: "I don't think you'll see him in the short term.
"Unfortunately something has flagged up with his ECG, which is the heart test. We've got top medical people here at the club now and we check all the players thoroughly from head to toe when they arrive.
"Unfortunately there's been a bit of a red flag with a heart issue so he's going to see some specialists in the coming weeks and we need to do more tests before we move forward.
"It's disappointing and frustrating but we'll have to manage and cope.
"The important thing is the player's health, which we'll obviously focus on first and foremost.
"Of course it's disappointing and frustrating for the player but I spoke to him yesterday and told him to keep smiling and be patient.
"We'll do everything we can to support him, get him in front of the right people with the right support, and hopefully he'll be back before too long."
Gerrard was speaking after the 2-2 draw with the Gunners which saw his Gers side twice pegged back, with goals from Leon Balogun and Cedric Itten cancelled out by Nuno Tavares and Eddie Nketiah.
"Large parts were okay,” he said. “We’ve got to take into consideration we’re playing against an elite team with elite players, and a lot of our good stuff was in front of Arsenal.
"I’d like us to be a bit more progressive once we break their press, people backing themselves and having courage to go on and do the next bit.”