Between Players and Doping, a Valet Seen as a Middleman Last year, Everth Cabrera was a promising young infielder hoping to make the San Diego Padres roster, but a nagging shoulder injury threatened to stall his big league career just as it was beginning. With spring training approaching and his shoulder not fully healed, Cabrera said, he made a grave mistake: he listened to Juan Carlos Nunez, an interpreter and aide who worked for Cabrera's agent. Cabrera said Nunez introduced him to the owner of an obscure anti-aging clinic in Coral Gables, Fla., who prescribed banned substances to him and at least 11 other players. The 12 players accepted 50-game suspensions Monday in the biggest single doping action in baseball history. All of those players were current or former clients of ACES, a prominent New York sports agency run by Sam and Seth Levinson, where Nunez had worked since about 2006. Nunez, a Washington Heights travel agent who became essentially a personal valet for the Levinsons" Spanish-speaking clients, has emerged as a key bridge, between the anti-aging clinic, Biogenesis, and a wide circle of professional baseball players, according to people with direct knowledge of baseball's doping investigation. The fallout has been swift. First, Nelson Cruz, an All-Star with the Texas Rangers who was suspended in the doping scandal, dropped ACES as his agents. Then Cabrera named Nunez as the gateway to Anthony P. Bosch, the discredited director of Biogenesis. And Tuesday, Michael Weiner, the executive director of the players union, pinned the blame squarely on Nunez. During an interview, Weiner deflected criticism from the players involved and from the Levinsons, saying that Nunez had played a central role in connecting the players with Bosch, and had acted without the knowledge of his bosses. "I think Nunez is a snake," Weiner said. What he did was horrible. Weiner added: "He should have the book thrown at him." A lawyer for Nunez declined to comment. A request to interview Nunez made through his lawyer was declined. Alex Rodriguez of the Yankees and Ryan Braun of the Milwaukee Brewers, two of the biggest stars punished in the Biogenesis scandal, had no known ties to Nunez or ACES. Rodriguez is appealing his 211-game suspension, while Braun last month accepted a 65-game suspension. Baseball investigators and national reporters have spent months scrutinizing Bosch and his troubled anti-aging clinic. But in the wake of Monday's suspensions, attention has turned to Nunez, 47, a former travel agent in Upper Manhattan who moved into a career on the lower rungs of baseball, far from the sport's corridors of power. A married father of two, Nunez owned American Worldwide Travel, an agency in the Washington Heights neighborhood that offered trips to the Dominican Republic, where he was born, among other destinations. Dominican baseball players frequented his business; Nunez's younger brother, Tirzon Nunez, briefly played minor league baseball. When an airline serving the Dominican Republic folded in 2003, Nunez was quoted in The New York Times describing his customers struggling to make it home for the holidays. About two years later, Nunez was involved in another business, American Worldwide Telecom, that distributed prepaid calling cards bearing the faces of major league players. The cards, which were not licensed by Major League Baseball, drew complaints from bodega owners, who claimed that the cards had less time on them than advertised, though at the time Nunez stood by his cards. Around 2006, the Levinson brothers at the ACES agency hired Nunez to work as a fixer and interpreter for Latin American players. He was licensed as a limited agent in 2010, but he was not allowed to negotiate players" contracts. He was more like a fixer. If the players needed anything - a ride, extra tickets to the game, a dinner reservation - they could call Nunez. And, apparently, if the players needed help recovering from an injury or gaining an extra step, they knew to call Nunez as well. Alain Delaquérière contributed reporting.