Based on the initial diagnosis, Green is believed to have suffered a sprained ankle, NFL Network Insider Ian Rapoport reported.
The receiver will undergo an MRI to confirm the initial diagnosis. If the MRI confirms a sprained ankle, Cincinnati is expected to be exercise serious caution with Green throughout the preseason.
Bengals coach Zac Taylor downplayed the injury following practice, telling reporters, "I think we'll let him get checked out. I don't think anything that's happened today is anything that... You don't want to assume anything, but I think we're going to be OK."
Green missed seven games last season with a right toe injury. He finished with a career-low 77 targets, 46 receptions and 694 receiving yards.
Just hours before practice began, Green sat down with NFL Network to discuss Cincinnati's potential on offense in Taylor's first year at the helm.
"There's really no limit for us," he said. "For us it's just everybody staying healthy."
Hopefully for Cincinnati, that will be the case come September.