Steve Bruce believes his former club Sunderland could be "in serious trouble" after it emerged the north-east club were fined for fielding striker Ji Dong-won in four Premier League games for which he was technically ineligible.
Sunderland were fined a six-figure sum after they made the Premier League aware that they did not have international clearance for the Korean player.
The club are confident they will not face further punishment and a Premier League source told Press Association Sport the rule breach was the "lowest level of administrative error", in that Ji was registered with the club but that Sunderland did not have his international transfer certificate.
The club were fined by the Premier League board in December but the issue has only now come to light.
Hull boss Bruce, who signed Ji when he was Sunderland manager in the summer of 2011, told a news conference on Friday : "That's pretty bizarre stuff that it's only surfaced now and he's played in four games.
"They should be in serious trouble, I would have thought."
Asked if he would expect a club fielding an ineligible player to be handed a points deduction, Bruce replied: "It's the first I have heard of it and it will be interesting, I would have thought so though."
Sources on Wearside say the club consider the matter closed and are confident they fulfilled their responsibilities when the administrative error came to light, and insist there is no ongoing investigation amid speculation that the relegation-threatened club could yet be docked points.
Sunderland currently lie in 19th place in the table, four points adrift of safety with just eight games to play.
Press Association Sport also understands club secretary Liz Coley left her job in December to take up a new position, but not as a result of the problem with Ji's clearance.
The 22-year-old South Korea international, who was registered with the Premier League and was included in the 25-man squad they released in August, made four appearances in the competition, as a substitute against Fulham, Southampton and Manchester United and from the start at Crystal Palace before the mistake was discovered.
Only one of those games, a 1-1 draw at Southampton on August 24, saw then manager Paolo Di Canio's side rewarded with a point.
However, Ji also played in the Capital One Cup second-round clash with MK Dons, which Sunderland won 4-2 on their way to the final.
The confusion appears to surround the striker's return to Sunderland after a loan spell with German Bundesliga club Augsburg last season.
His spell back in English football, however, proved brief and he returned to Augsburg, this time on a permanent deal, in January this year having made just two more senior appearances under current boss Gus Poyet.
Ji initially joined the Black Cats from Chunnam Dragons for £2million in June 2011 during Bruce's spell in charge, but started only six senior games for the club, although he did score a memorable winner against Manchester City on New Year's Day 2012.