Floyd Mayweather Jr.'s return to the ring May 4 at MGM Grand in Las Vegas remains in negotiation, with Gilroy's Robert Guerrero the most likely opponent, the man negotiating the bout said.

Richard Schaefer, the Golden Boy Promotions executive who's helped promote all of Mayweather's fights since 2007, said Thursday, "I know 100 percent that Floyd will be on that card."

Mayweather (43-0) last fought in May, defeating Miguel Cotto by unanimous decision.

While nothing is signed, according to Schaefer, Guerrero emerged as the opponent in the WBC welterweight title fight by knocking down Andre Berto twice in a Nov. 24 bout that Guerrero (31-1-1) won by decision in Ontario.

Schaefer would only say he's made "a lot of progress" on the deal and is "working on this diligently."

MSL

Earthquakes striker Marcus Tracy is among the players appearing Monday at Soccer Night in Newtown, a charity event for residents of the Connecticut town that is reeling from last month's killing spree at Sandy Hook Elementary School.

Tracy, who joined San Jose in September after the club won a weighted lottery to sign him, grew up in Newton and his mother once taught at Sandy Hook.

"It hurts you as a resident of Newtown that something like this could happen, so just try and imagine how parents, brothers, sisters and spouses are feeling right now," he told a reporter last month.

Newton residents and members of the Newtown Youth Soccer Club will have a chance to meet MLS and U.S. national team stars and play in games. Tracy will be joined by Landon Donovan, Brad Davis, Brian Ching, Matt Reis, Cobi Jones, Alexi Lalas, Mia Hamm and Connecticut native Kristine Lilly. Former Stanford star Bobby Warshaw (FC Dallas) and Salinas' David Estrada (Seattle Sounders) also plan to appear.

The event is the brainchild of Houston Dynamo president Chris Canetti, a native of Guilford, Conn.

Arena Football

CBS Sports Network's first season of coverage includes 19 regular-season games, starting with champion Arizona hosting Philadelphia on March 23 in a rematch of ArenaBowl XXV. Games featuring the SaberCats are April 6 at Arizona (5:30 p.m.), June 1 at Spokane (7 p.m.) and July 13 at Pittsburgh (4 p.m.). CBS will air ArenaBowl XXVI on Aug. 17.

Colleges

The Santa Clara men's basketball game with No. 10 Gonzaga at the Leavey Center on Saturday is a sellout. The game will be televised live on CSNCA. Tipoff is 5 p.m.

Mixed martial arts

UFC will return to HP Pavilion on April 20 for UFC on Fox 7. The fighters haven't been announced yet.

Staff writer Elliott Almond and wire services contributed to this report.