In 1987, Manfred began working with Major League Baseball (MLB) during collective bargaining. During the 1994–95 MLB strike, he served as outside counsel for the owners. He joined MLB on a full-time basis in 1998, serving as the Executive Vice President of Economics and League Affairs. Manfred negotiated MLB's first drug testing agreement with the Major League Baseball Players Association (MLBPA) in 2002, and represented MLB in negotiations with the MLBPA when forming new collective bargaining agreements in 2002, 2006 and 2011