MLB suspended Alex Rodriguez 211 games for violating the Joint Drug Agreement and the Collective Bargaining Agreement. The league alleges that Rodriguez procuring banned drugs from Biogenesis from 2010-2012, then interfered with the league's investigation of the Miami-area anti-aging clinic.
Bosch is expected to be the key witness to support the evidence MLB has acquired, according to the New York Daily News. He has been cooperating with the commissioner's office since last spring, and will corroborate evidence that Rodriguez repeatedly violated the JDA.
Rodriguez and his lawyers plan to attack Bosch's credibility and cross examine him. Bosch only agreed to cooperate with MLB if the league dropped a lawsuit against him, help cover his legal expenses and indemnify him from litigation that his testimony could cause. Rodriguez's lawyers will attempt to paint Bosch as untrustworthy because he has been paid off.