World Boxing Council champion Jose Luis Castillo (52-6-1, 46 KOs) and World Boxing Organization titleholder Diego Corrales (39-2, 32 KOs) are the two best lightweights in the world. On Saturday night, they’ll meet in the ring, courtesy of Showtime.

Last year, Showtime decided that, rather than televise boxing on a random schedule, it would feature the best fights it could within its budget on the first Saturday of each month. So far, the results have been encouraging. Zab Judah’s February 5 knockout of Cory Spinks in a 147-pound title-unification matchup was a great fight. Jean-Marc Mormeck’s April 2 decision over Wayne Braithwaite in a cruiserweight title-unification bout was almost as good. And there’s a realistic chance that Castillo-Corrales will top them both.

Castillo, 31, is a skilled, durable fighter with victories over Julio Diaz, Joel Casamayor, and Juan Lazcano in his past three fights. Outside of two defeats by decision at the hands of Floyd Mayweather Jr., he hasn’t lost since 1998.

Corrales, 27, was stopped by Casamayor on cuts in 2003. But in two fights since then, he won a return bout against Casamayor by decision, and knocked out the previously undefeated WBO champion Acelino Freitas. The only other loss of Corrales’s career was a 10th-round stoppage at the hands of Mayweather in 2001.

The consensus belief is that Corrales hits harder, but Castillo takes a better punch. That’s based in part on the fact that Mayweather knocked Corrales down five times and couldn’t floor Castillo in 24 rounds of boxing. Casamayor also hurt Corrales.

But Corrales is unfazed by the talk. Last week, at a press conference, he was asked how he felt about the fact that some people were picking Castillo because they thought that Jose Luis had a better chin.

“If they believe that, then that’s okay,” Corrales answered. “My chin has stood up against some of the best. It doesn’t bother me at all. We’ll see exactly what happens in a week.”

Castillo-Corrales is too close to call. Most likely, Corrales will box cautiously early and take more risks as the action progresses, loading up his punches in the later rounds. Castillo is expected to move inexorably forward all night long.

In the first televised bout of the evening, Juan Manuel Marquez (43-2-1, 33 KOs) defends his World Boxing Association and International Boxing Federation 126-pound titles against Victor Polo (34-4-3,24 KOs).Marquez is a clear favorite, and appropriately so: He’s an elite fighter with victories over Derrick Gainer and Robbie Pedon, in addition to a draw with Manny Pacquiao.

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On occasion, an unseen corner of the boxing world is illuminated for the unknowing. “Shadow Boxers” (Stone Creek Publications, $39.95), a marvelously produced coffee-table book featuring photographs by Jim Lommasson, does just that.

“Shadow Boxers” takes readers into the gyms where young fighters learn their trade. The photographs are accompanied by a series of essays, the best of which are written by Katherine Dunn.

“Boxing gyms are more than training facilities,” Dunn writes. “They are sanctuaries in bad neighborhoods for troubled kids and shrines to the traditions of the sport. The gym is home. For many, it’s the safest place they know.”

And Dunn is on target when she notes ironically, “A boxing gym is a place where men are allowed to be kind to one another.”

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Undisputed middleweight champion Bernard Hopkins (46-2-1, 32 KOs) has signed for a fight that some observers think is his biggest risk since losing to Roy Jones 12 years ago.Hopkins,40,will take on 26-year-old Jermain Taylor (23-0, 17 KOs) on July 16 at the MGM Grand in Las Vegas. Taylor has been marketed by HBO as the “heir apparent” in the middleweight division. He’s big and strong, but has never faced a fighter with skills approximating those of Hopkins. It will be an intensely interesting fight.