Hall suffered a concussion during Saturday's preseason contest against the Jets, Art Stapleton of The Record reports.
The Giants inked Hall to a contract in early August to bolster their depth at cornerback, but he's worked as a free safety in recent practices due to injuries befalling each player at the position. With his diagnosis known, there's no telling when Hall may be able to return to the field.
During 7-on-7 periods, Hall received extensive work at free safety alongside strong safety Landon Collins in the base and nickel defenses, the Newark Star-Ledger reports.
With Darian Thompson (shoulder) sidelined for at least a week, the Giants need to find a free safety, and the veteran cornerback could be the solution. If Hall were to wind up starting, he'd have some IDP upside.
Hall (back) signed with the Giants on Thursday, Dan Salomone of Giants.com reports.
Hall spent the entirety of his nine-year career thus far in Cincinnati, where he racked up 470 tackles, 26 interceptions, 112 passes defensed, and five forced fumbles. The 31-year-old underwent back surgery earlier this offseason that may hamper his availability throughout training camp, but he's set to provide a veteran presence in the Giants' secondary while Eli Apple, Janoris Jenkins, and Dominique Rodgers-Cromartie lead the cornerback corps.
Leon Hall underwent back surgery earlier in the offseason, NFL.com's Chris Wesseling reports
According to the source, the surgery was to correct an issue with a disc in his back that had nagged him late in 2015. Hall isn't the cover corner he used to be, but can still patrol the slot effectively, as evidenced by yet another above-average coverage grade per ProFootballFocus.com for his performance last season. In fact, there isn't a season in which Hall hasn't graded out as at least above-average. Nonetheless, the Michigan product is entering his 10th season in the league, and had already experienced an Achilles tear in both 2011 and 2013 before aggravating his back. Coupled with the likelihood of him taking his time to land one last pay day, it may still be a while before Hall finds a new home.