Roger Clemens had just been yanked from the mound after a terrible outing, giving up five runs on six hits and failing to record an out in the third inning. It was a big game on a major stage: the 1999 American League Championship series that pitted his New York Yankees against their archrival Boston Red Sox.

Shortly after being pulled from the game, Clemens sulked his way to the visitor’s locker room. There, the Yankees’ general manager, Brian Cashman, found his star pitcher sitting dejected and defeated in front of his locker.

“I need McNamee,” the then 37-year-old pitcher told his GM. “Get me McNamee.”

That scene — and others he used to characterize the relationship between Clemens and McNamee, which are described below — was related Monday by assistant U.S. Attorney Steven Durham during opening statements in Clemens’s trial on charges of lying to Congress when he testified during hearings in 2008 that he had never taken performance-enhancing drugs.

McNamee, of course, is Brian McNamee, Clemens’ strength coach and a key prosecution witness who claims that he injected Clemens with such substances on numerous occasions in 1998, 2000 and 2001.

That moment in the Yankees’ locker room came at a key point in their relationship — and one that would help set in motion the downfall from grace of one baseball’s most decorated pitchers.

The scene also illustrates a narrative that Durham and prosecutors will seek to spin out during the four-to-six week trial — that of a hyper-competitive aging superstar who turned to a friend, McNamee, to give him that extra edge he needed to remain competitive in the big leagues. It’s the kind of story arc that even a juror who knows nothing about sports can follow.

According to Durham, the pair became close when they crossed paths in early 1998 when Clemens was pitching for the Toronto Blue Jays and McNamee was the team’s strength coach. Clemens was struggling to recover from injuries and not playing particularly well — age appeared to be catching up with him, according to Durham.

That’s when Clemens and McNamee began talking about the benefits of anabolic steroids, a drug that can help athletes build muscle, recover more quickly from injuries and lubricate joints.

Soon, McNamee was visiting Clemens’ apartment and injecting the player with the substance. The season turned into a success for “the Rocket” — he won 20 games, recorded an era of 2.65 and notched his fifth Cy Young award.

In 1999, Clemens was traded to the Yankees, and he asked Cashman to hire McNamee. But the Yankees’ general manager demurred. The season turned into a bust for Clemens, though the Yankees would eventually win the World Series. He won only 14 games and had a 4.6 earned-run average. By the playoffs, people were wondering if he had lost his edge.

Then he appealed to Cashman, who is expected to testify during the trial, in the Fenway Park locker room. The next season, McNamee was on the Yankees’ payroll. That year and in 2001, McNamee injected Clemens with steroids or Human Growth Hormone, another perforamnce-enhancing substance

And Clemens kept pitching, making four more All-Star teams (he played in 11 All Star games) while notching two more Cy Young awards. He retired in 2007 at the age of 44.

Expect Clemens’ defense team to work hard to deconstruct Durham’s narrative — starting Tuesday morning when they get to address jurors for the first time.

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