Cota received the penalty under the Major League drug program, despite not being on a Major league roster since June 15, 2007, when he was released by the Pirates.
"I want to make it clear that I did not use any banned substances in order to improve my performance," Cota said in a statement released by the Players' Association. "In July 2007, I had season-ending surgery performed on my left shoulder. During this past winter, while I was a free agent, my shoulder was slow to heal. I took substances that were prescribed for me by a doctor in Mexico.
"I believed I was taking anti-inflammatory medication that would help my shoulder heal. What I did not know at the time was that these substances would cause me to test positive under MLB's drug policy. I have learned that I should only rely on medical care provided by U.S.-based doctors. I apologize to my family, my teammates, the fans of Major League Baseball and the Rockies' organization. I know I will be more careful in the future."
Cota, 29, is hitting .333 with eight RBIs in 15 games for the Sky Sox this season. He played parts of the past seven seasons with the Pirates, hitting .233 with 12 homers and 61 RBIs in 196 career games.
Cota signed a Minor League contract with the Nationals last November and was released in March. Cota then signed a Minor League contract with the Rockies.
He is the second player penalized this year under the Major League policy. Giants catcher Eliezer Alfonzo was suspended for 50 games on April 30.
Andy Jasner is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.