Former HBO Sports exec Ross Greenburg joins Showtime to promote Floyd Mayweather-Robert Guerrero bout

Showtime on Tuesday announced a full slate of programming to support its upcoming May 4 pay-per-view broadcast of the Floyd Mayweather Jr.-Robert Guerrero fight from Las Vegas.

To fully appreciate the significance of what Showtime announced, though, requires a bit of a history lesson.

In January 2011, Top Rank's Bob Arum struck a deal with CBS president Les Moonves to bring Manny Pacquiao's fight with Shane Mosley to Showtime pay-per-view on May 7, 2011.

That move caught HBO officials off-guard and, in many ways, was responsible for Ross Greenburg resigning from his post as president of HBO Sports the following July.

A month later, Arum then announced that Pacquiao would return to HBO Pay-Per-View for what was then his third fight with Juan Manuel Marquez, which was held Nov. 12, 2011. But about a month before that fight happened, HBO Sports hired Ken Hershman away from Showtime to replace Greenburg.

Last month, Mayweather, the top pound-for-pound boxer in the world, announced he was leaving HBO to sign a lucrative deal with Showtime. And with Mayweather's May 4 fight at the MGM Grand Garden in Las Vegas against Guerrero the first bout under that deal, Showtime on Tuesday announced it had hired who else other than Greenburg to serve as executive producer on two major projects to promote the fight.

Greenburg will serve as executive producer of "Mayweather," a one-hour documentary film on Mayweather's career that will be broadcast on CBS in prime time at 8 p.m. ET/PT on April 27. Greenburg will also serve as executive producer of "All Access," the behind-the-scenes series that will trail Mayweather and Guerrero as they prepare for the fight. That series begins April 10 on Showtime, with a new episode every Wednesday.

But Showtime is going all-out to make its Mayweather debut a success. On April 3 at 10 p.m. ET/PT, it will broadcast a one-hour documentary called "30 Days in May," that will document Mayweather's 2012 stint in jail. It will include never-before-seen footage as well as the only interviews Mayweather has given on the topic.

Showtime also plans to re-air a series of Mayweather's and Guerrero's best fights. All of the Mayweather fights it will replay -- matches against Oscar De La Hoya, Ricky Hatton, Marquez, Mosley and Victor Ortiz -- originally aired on HBO Pay-Per-View. Showtime will not use the HBO announcers, though. Its rebroadcasts will use the international broadcast announcers.

Showtime will also live stream the weigh-in May 3 and will broadcast a live pre-fight show on May 4.

Moonves was serious about upgrading Showtime's boxing content after losing Pacquiao back to HBO. He's responded by dramatically increasing Showtime's boxing budget and giving Showtime Sports general manager Stephen Espinoza wide latitude to push the Mayweather-Guerrero bout over all of the company's media properties.

Adding Greenburg was a master stroke, because he is a brilliant documentarian. He created the boxing preview show concept while at HBO, where it was dubbed "24/7." Those shows helped Mayweather to become the sport's biggest star.

Now, Greenburg will work to help his one-time bitter rival vanquish his long-time former employer.

As Don King might say, only in boxing.