MLB commissioner Bud Selig, right, and MLB vice president of...

MLB commissioner Bud Selig, right, and MLB vice president of labor relations Rob Manfred react during a news conference announcing a five-year collective bargaining agreement in New York. Credit: AP, 2011

Major League Baseball's chief operating officer, Rob Manfred, testified at Alex Rodriguez's arbitration hearing Thursday, a person familiar with the process said.

The sworn testimony of the sport's second-highest-ranking official in the confidential proceeding came on the seventh day of Rodriguez's appeal of his 211-game suspension for alleged violations of the joint drug agreement and Basic Agreement related to MLB's probe into Biogenesis, the now-shuttered anti-aging clinic in Miami that allegedly supplied players with steroids.

Attorneys for Rodriguez were expected to ask arbitrator Fredric Horowitz to block or limit Manfred's testimony, a source had said, based on his role as a member of the arbitration panel, which also includes Major League Baseball Players Association representative David Prouty.

Manfred's testimony, which concluded after one session, was expected to dispute the contention that Bosch was paid for cooperating with MLB. It was not immediately known if Manfred was cross-examined by Rodriguez's attorneys.

Manfred has been with MLB since 1998. Sports economist Andrew Zimbalist, a consultant to MLB who has known Manfred since 1990, said MLB considers him its "drug czar. The go-to guy for drug-related issues."

Manfred, widely believed to be a prime candidate to succeed retiring commissioner Bud Selig, coordinated the investigation into Biogenesis.

Zimbalist said there is a bigger issue to Manfred than winning the arbitration.

"Anybody who is in an arbitration like this always wants their side to prevail as much as possible," Zimbalist said, "so on that level it matters . . . I think they would like to have a victory over A-Rod. I think they feel A-Rod has been playing games with baseball for a long time and that he's playing games with lawyers right now.''

When Rodriguez filed suit against MLB on Oct. 3 , claiming a "witch hunt," Manfred told Newsday, "The suit is so flawed from a legal perspective and so unfounded from a factual perspective, it does not affect our thinking on any topic."

Notes & quotes: New York state Sen. Ruben Diaz (D-Bronx) joined with Assemb. Gabriela Rosa (D-Manhattan) to support Hispanics Across America in protesting Rodriguez's suspension.

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