Portugal and Luxembourg filed protests with UEFA against Ukraine fielding Brazil-born forward Junior Moraes in European Championship qualifying games.
UEFA says it opened disciplinary proceedings against Ukraine for a possible breach of player eligibility rules. No date for a hearing was confirmed.
Moraes was this month granted citizenship in Ukraine where he has played for most of the past seven seasons, currently for Shakhtar Donetsk.
FIFA rules allow players to acquire a nationality if they live continuously in the country for five years.
Ukraine risk losing four points and forfeiting both games as 3-0 losses if the 31-year-old Moraes is judged to have been ineligible.
Ukraine currently leads their Euro 2020 qualifying group after drawing 0-0 at Portugal and winning 2-1 at Luxembourg in the past week.