Benfica, which has the largest fanbase in Portugal, re-elected Luis Filipe Vieira as their president on Saturday after he pledged to move the broadcasting of league matches to the club's television channel to boost revenues.
The Lisbon club's move has made TV operators in the profitable business jittery given Benfica matches top television audiences in Portugal week in, week out.
In Portugal, around 70 percent of the broadcasting rights revenues estimated at around 75 million euros per season go to the so-called "big-three" clubs - Benfica, Sporting and Porto.
As in neighbouring Spain, TV contracts in Portugal are negotiated on a club-by-club basis, unlike in the Premier League and Serie A, where collective bargaining deals are struck.
Market analysts say the club's large viewing base means that, after matches move to Benfica TV, the club will not be able to negotiate TV rights with one pay-TV operator alone because it would violate fair-competition rules.
"We expect the anti-trust authority to step in and make sure the broadcasting of Benfica TV may be done by all pay-TV operators," analysts at BPI bank in Lisbon wrote in a research note on Tuesday, saying the regulator will force Benfica to give all five of Portugal's operators a fair chance to bid.
Many Portuguese football fans have expressed their unhappiness about there being no league matches on open channels this season, as they have to pay an expensive fee to watch them on specialised channels.
Benfica TV comes in cheaper cable TV packages offered by Portugal Telecom and Sonaecom, but the channel is not available in other operators.
Currently, one operator, Olivedesportos' PPTV, has the rights to all domestic professional football games and platforms. They are subsequently re-sold to Sport TV channel, jointly-owned by Olivedesportos entrepreneur Joaquim Oliveira and telecom company Zon.
In March, Benfica said no to a 111 million euros proposal from Olivedesportos for the broadcast of their home matches between 2013 and 2018.
Benfica and the anti-trust body were not available to comment.