Sky may be forced to break the bank to hold on to its Barclays Premier League broadcast rights in the next auction, it has been suggested.
Matthew Walker, a Media Analyst with investment bank Nomura, described the bidding process - scheduled for 2015 - as a "must-win" for Sky, as reported by the Guardian.
The broadcaster currently airs 116 live matches for English football's top flight each season, compared to BT Sport's 38, which includes 18 of the top-pick games.
However, BT Sport recently outbid Sky to secure UEFA Champions League and UEFA Europa League coverage from 2015-16 on a three-year deal.
The £299 million per year BT Sport will pay for European club football far eclipses the £400 million paid by Sky and ITV over three years under the current TV deal.
Mr Walker said BT Sport has demonstrated through its actions that it is "not content to be the number two sports service" in Britain.
He added that this has big implications for the next Premier League auction in mid-2015, with BT sure to target additional fixtures.
This will impact on the amount Sky will have to pay to retain its existing rights, Mr Walker noted.
"We raise our inflation assumption to 60 per cent from 40 per cent (up another £156 million per annum)," he said.
"Sky cannot afford to be [financially] disciplined on this one."