Kelechi Iheanacho was taken off with injury, in the second half of Manchester City’s Champions League second leg play-off against Steaua Bucuresti.
The Super Eagles looked to have picked up a hamstring injury, as he tried to chase a ball through.
Medics attended to him on the pitch, before taking him off on a stretcher, after discovering he could not continue.
It is a huge blow to City and especially to Iheanacho, who was making only his first start under new manager, Pep Guardiola.
City won 1-0 on the night, qualifying for the Champions League proper on a 6-0 aggregate.
Although the extent of the injury is not known yet, Iheanacho is likely to miss Nigeria’s Africa Cup of Nations qualifier against Tanzania in September.