Napoli was penalized two points in the Serie A standings for match-fixing after its former goalkeeper confessed to arranging the result of a game three seasons ago.
The sentence by the Italian football federation's disciplinary committee on Tuesday dropped the southern club from a tie for third place into fifth position, 10 points behind league leader Juventus .
The penalty put a severe dent in Napoli's aim of winning the Serie A for the first time since Diego Maradona led the team to titles in 1987 and 1990.
Also, current Napoli captain Paolo Cannavaro and defender Gianluca Grava were each banned for six months for failing to report the fix.
Cannavaro is the younger brother of former Italy captain Fabio Cannavaro.
Napoli was also fined €70,000 ($92,000).
Both players, along with Napoli, deny any wrongdoing.
The keeper, Matteo Gianello, confessed to prosecutors that he attempted to fix the match between Sampdoria and Napoli on May 16, 2010.
Sampdoria won 1-0 with a goal from current AC Milan player Giampaolo Pazzini in the 51st minute. It was the final round of the season and the victory secured Sampdoria fourth place and a spot in Champions League qualifying.
Gianello was banned for three years and three months.
Appeals were expected.
Last week, federation prosecutor Stefano Palazzi requested a one-point penalty for Napoli and a €100,000 ($129,300) fine for the club, a 39-month ban for Gianello and nine-month suspensions for Cannavaro and Grava.
Also on Tuesday, third-division Portogruaro was penalized two points for fixing a May 2011 match with Crotone, while Crotone was cleared of wrongdoing.
Napoli becomes the fifth Serie A club docked points this season for fixing - although the first to be penalized in midseason. Siena was already docked six points, Atalanta two, and Sampdoria and Torino one each.
Juventus coach Antonio Conte returned this month from his four-month ban for failing to report fixing when he managed Siena two seasons ago.
The federation's justice system provides two levels of sentences: The disciplinary committee's initial verdict and an appeal. Sentences can then be appealed to a national sports arbitration court, which has the final word.
At least 50 people have been arrested in Italy for match-fixing since the middle of last year, with scores more under investigation by prosecutors in Cremona, Bari and Naples.