The Pamplona-based outfit's official front page was changed by computer experts, who re-wrote the headline news and replaced it with a story that suggested two of the club's most consistent performers had left.
Early on Wednesday morning the news appeared that Nekounam and Masoud had been involved in a bar brawl and the Primera Division side had chosen to release the pair.
Hackers expertly posted the story, which some agencies and media outlets took seriously, and the club are now having to reinforce their firewalls and defences.
"Club Atletico Osasuna were obliged to rescind the contracts of the players Masoud Shojaei and Javad Nekounam after an altercation involving these players in a bar in Pamplona," the fake story read.
"The decision was taken in the early hours of the morning after a unanimous vote by the C.A. Osasuna board of directors."