The commissioner's office said the 38-year-old right-hander tested positive for Clenbuterol. In November 2006, while with the New York Mets, Mota was suspended for the first 50 games of the next season.
"We won't have Mota for a while. It is what it is, and you move on," manager Bruce Bochy said before the Giants began a three-game series against the Dodgers. "If we get into a situation where we need a pitcher, we're going to have to make a change. Right now we're going with 11 pitchers, and if we have to adjust, we will. We've got some pretty good options, we think, and Brian (Sabean) and I will continue to talk about them."
Mota's agent Adam Katz said in a statement that the Clenbuterol was in children's cough syrup.
"Players are responsible for what they put in their bodies. Guillermo understands that," Katz said. "A 100-game suspension for taking a children's cough medicine that contains trace amounts of a prohibited substance, which is what happened here, is severe and unfair and does not reflect the intention of the Joint Drug Prevention and Treatment Program. We will appeal it."
The Major League Baseball Players Association filed a grievance challenging the suspension that will be heard by an arbitrator. Under baseball's drug agreement, grievances for initial positive tests are heard before a suspension is announced but cases involving second or third positives are argued after the penalty is made public.
Outfielder Manny Ramirez and catcher Eliezer Alfonzo are the only previous players to twice test positive. No player has tested positive a third time, which would result in a lifetime ban.
Alfonzo was suspended for 50 games in 2008 while with San Francisco and for 100 games last September while with Colorado. By the time Mota's suspension is over, the Giants will have 34 games left on the schedule.
Mota was 0-1 with a 5.06 ERA in nine games for the Giants this year. This is his 14th season in the majors. He has been a setup man and middle reliever throughout his career. He is 39-45 with 10 saves in 726 games while playing with Montreal, the Los Angeles Dodgers, Florida, Cleveland, the New York Mets, Milwaukee and San Francisco.
"I don't much about what happened. But we lost a guy and he's done for a while, so losing him is a big blow," pitching coach Dave Righetti said. "He's always been ready to pitch, and he's been effective whether he's a long guy or a short guy. Sometimes we've used him in the seventh, sometimes to finish a game. So we have a lot of confidence in him. He brings a veteran presence that comes to work every day ready to go, and he shows these guys how to work. That's the reason we keep bringing him back."
This is Mota's third season with the Giants. He was with the Mets when he previously suspended and missed the first 50 games of the 2007 season. At the time of that suspension, the identity of a substance causing a positive test is being made public under the new collective bargaining agreement.
Clenbuterol acts as a stimulant, increasing heart rate. In medicine, it is used to treat asthma. Like some steroids, the drug also has anabolic effects. Athletes and body builders use it to build muscle and burn fat.
Ramirez served a 50-game suspension while with the Los Angeles Dodgers in 2009, then retired rather than serve a 100-game ban while with Tampa Bay last year. Because Ramirez sat out nearly all of 2011, his penalty was cut to the first 50 games of this season under an agreement between management and the union that allowed him to end his retirement. He agreed to a minor league contract with Oakland.
The Giants filled the roster spot by activating outfielder Aubrey Huff, who was on the disabled list because of an anxiety disorder that began in his New York hotel room early on April 23 before the Giants played a doubleheader with the Mets.
With top hitter Pablo Sandoval sidelined for four to six weeks after undergoing surgery Friday on a broken hamate bone in his left hand, the Giants are short-handed offensively, too. And Bochy believes Huff can give the team a lift.
"I'm excited, and I think Aubrey is, too," Bochy said. "He gives us an experienced bat and a guy that can hit in the heart of the order, but we've got to get him going. ... He got out of synch his last two or three games, but if we can get him going, he gives this club what we need — a guy that can drive in runs."