"Showtime has not been in the PPV business as much in recent times as HBO has," said Stephen Espinoza, general manager of Showtime Sports. But with Mayweather on board, he expressed cautious confidence in his network's progress.
"I don't think anyone can realistically, objectively say that the two networks aren't at least on par with each other," Espinoza said. "I wouldn't argue with anyone who says that we have pulled ahead."
Showtime's boxing resurgence has also been facilitated by CBS CEO Les Moonves, a boxing aficionado, he said.
"He is a huge boxing fan," Espinoza said. "He attends fights regularly in Los Angeles, big fights and small fights. I could not have done a deal of the scale that we did with Mayweather without his approval and enthusiasm."
Mayweather Promotions CEO Leonard Ellerbe said he feels that enthusiasm.
"Showtime and CBS made it very clear that they wanted to be in the Mayweather business," he said. "It's the best move that they could have made."
Ellerbe said that Mayweather's confidential deal with Showtime has vaulted the network into the PPV lead, and he predicted record-breaking gross revenue for Saturday's fight.
"HBO has been the premier network for so many years. Now Showtime has not only caught up with them, they've surpassed them," Ellerbe said. "We've got a good expectation of surpassing the gross that we did in the de la Hoya fight."
He declined to specify how much the fighter stands to make from the contest but called the contract "very lucrative." Various estimates put Mayweather's likely payout at more than $40 million.
Alvarez, a rising star with a huge, dedicated following of his own, also is set to receive a big payout.
While insiders point to Saturday as the consensus pick for the year's most anticipated boxing event, HBO will answer with two high-profile fights in October and November, one showcasing champion Juan Manuel Márquez, and the other featuring global superstar Manny Pacquiáo.
—By CNBC's Adam Molon. Follow him on Twitter at @cnbcmolon