NEW YORK -- The video footage on ESPN of Roger Clemens and Andy Pettitte working out together is at once striking and stirring: a pair of driven athletes pushing limits with a variety of exercises, challenging their bodies to the next level.

In the background, barking out commands, was Brian McNamee, a little-known personal trainer employed by both star pitchers. But with the release of the Mitchell Report on Thursday, McNamee is no longer in the shadows.

The former Yankees employee's bombshell allegations comprised a significant portion of former Sen. George Mitchell's investigation into the use of performance-enhancing drugs in baseball.

An assistant strength and conditioning coach with the Yankees in 2000-01, the 40-year-old McNamee drew the interest of the Mitchell investigation when four checks written to Kirk Radomski, a former Mets clubhouse attendant and accused steroid dealer, were uncovered.

By agreeing to cooperate with the commission and provide testimony, McNamee is avoiding possible federal prosecution for drug distribution, according to the Mitchell Report.

Through his agreement with the U.S. Attorney's office, McNamee consented to three separate interviews with the Mitchell investigation, one in person and two by telephone. Federal prosecutors and agents from the FBI and IRS also participated, and according to the Report, McNamee was advised each time that he could face criminal charges if he made any false statements during the interviews.

Clemens' attorney, Rusty Hardin, said on Thursday in a statement that he took umbrage with the fact that federal authorities had used the threat of criminal investigation against McNamee to help a private business investigation.

"I am extremely upset that Roger's name was in this Report," Hardin said in the statement, "based on the allegations of a troubled and unreliable witness who only came up with names after being threatened with possible prison time."

But if anything is clear regarding the Mitchell Report and the sequence of events that concerns Clemens, it is that McNamee not only enjoyed a close relationship, but also the right-hander's trust.

An athletic administration major and baseball player at St. John's University from 1985-89, McNamee grew up in the Rockaway section of Queens, working as an undercover New York City police officer from 1990 until May 1993, when he was hired as a Yankees batting-practice pitcher and bullpen catcher.

McNamee was released from those duties after the 1995 season, but he remained in sports by obtaining a Master's degree in sports science from Long Island University. He trained non-baseball, Olympic-caliber athletes until 1998, when he was hired by the Blue Jays as the team's strength-and-conditioning coach.

It was with Toronto that McNamee and Clemens began their association, and according to the Mitchell Report, where they first began activity with performance-enhancing drugs. Clemens, then 36, kept an apartment at Skydome -- now known as Rogers Centre -- while pitching for the Blue Jays and was, in the infamous words of former Red Sox general manager Dan Duquette who traded him to Toronto, "in the twilight of his career."

The Rocket's resurgence coincided with the time frame when McNamee testified that he injected Clemens with steroids on multiple occasions on those premises, gleaning terrific results.

Clemens finished the second half of the 1998 season with 11 victories, and according to McNamee's testimony in the Report, he bragged to McNamee that the injections were working -- he was now able to work out longer and harder than before. The proof was in the stats.

"Whenever you read something that takes place on Blue Jays' turf, you say that's too bad," Blue Jays president and CEO Paul Godfrey said on Thursday night. "I'm disappointed, certainly. But again, I have to balance this by saying these are allegations at this time. I'm sure that the Commissioner's Office will examine these allegations and determine whether they have merit or not."

When Clemens was traded to New York in February 1999, hunting for the World Series ring that so far had eluded him, McNamee was apparently one piece of his Toronto life that he wanted to keep. In the aftermath of the Yankees' 25th World Series championship, McNamee came aboard, joining the Yankees as an assistant strength-and-conditioning coach reportedly at Clemens' urging.

With McNamee by his side, Clemens was still among the Major Leagues' most dominant pitchers, rolling back the odometer of time and helping New York win back-to-back titles in 1999 and 2000.

"I've had more than a handful [of trainers], and Mac is a definitely the best," Clemens told the New York Post in March 2002. "The reason why my velocity continues to be what it is because of what we're doing behind the scenes."

Clemens' workout programs of long runs, sprints, weightlifting and abdominal training, plus a specific diet regimen, were widely credited at the time for the Rocket's success, but few questions were asked further -- not that Clemens or McNamee likely would have volunteered.

In an Oct. 1, 2000, New York Times article, McNamee, who served as Clemens' personal trainer for one to two weeks during Spring Training and a few times during the season, personally took issue with accusations of steroid use among Major League players.

"The suggestion that steroids are the answer to the increased strength, recovery from injury and the improved performances of today's players is just wrong," McNamee said then.

"Yes, the players today are stronger, faster and smarter than their predecessors. But their superiority is not because of steroid use, but because of the advancement in sports-specific science and commitment of the organizations to strength, conditioning and nutrition. To suggest otherwise is irresponsible and disrespectful."

Under the scope of the Mitchell investigation, McNamee testified that in 1998, 2000-01, he injected Clemens with both steroids and human growth hormone (HGH) on numerous occasions.

McNamee was dismissed by the Yankees after the 2001 season, when he was investigated by St. Petersburg, Fla., police under allegations of sexual assault at the Yankees' hotel, a case that was eventually not pursued.

Yet he continued to have an impact on some of their players. McNamee worked extensively with Clemens and trained the right-hander's close friend, Andy Pettitte, at Clemens' Houston-area home, and he also worked with other Major League players, including infielder Chuck Knoblauch, also named in the Mitchell Report. McNamee testified that he injected Knoblauch seven to nine times with HGH.

In another section of the Report, McNamee is listed as the person who supplied and injected Pettitte with human growth hormone, allegedly doing so in 2002 while Pettitte rehabilitated tendinitis in his pitching elbow. McNamee said that, around the time of the BALCO investigations, he advised Pettitte not to go out of his way to bring up performance-enhancing substances to reporters, but that he was free to say what he wanted if asked.

In the Mitchell Report, McNamee said he was "a direct eyewitness and a participant in alleged illegal use by three players whom he served as a personal trainer."

McNamee continued a relationship with Pettitte that at least extended through the 2006 season, even though McNamee's name surfaced in a Los Angeles Times report that named McNamee as involved in former Major Leaguer Jason Grimsley's case involving amphetamines, steroids and human growth hormone.

Though he initially denied involvement, McNamee testified to the Mitchell investigation that he had even discussed steroids with Grimsley in the Yankees' bullpen.

"Grimsley showed [McNamee] a white bottle he said he had received from a pharmacist in Seattle," the Mitchell Report said. "Grimsley said the substance was 'Winni 5,' which McNamee understood to be Winstrol tablets at 5 milligram dosage. McNamee advised Grimsley that steroids, taken orally, could be toxic."

Shortly after the Times report, McNamee told SI.com that his reputation had been significantly impacted and painted a picture of opportunities drying up. Players were not calling for a personal trainer, a teaching opportunity at St. John's University had faded away and deals with fitness facilities and nutritional companies were vanishing.

In fact, it seemed only tried-and-true clients such as Clemens and Pettitte were standing by him.

"No one's concerned about Brian McNamee or how it affects my life," McNamee told SI.com in November 2006. "They just want to use me to get to them [Clemens and Pettitte]. And I'm the one getting hit by the bus. I got hit and I'm still standing there, and the bus has kept going."

At least, until now. On a conference call with reporters on Wednesday, Pettitte said that he had not worked out with McNamee recently.

"I have not -- not at all this offseason," Pettitte said. "I sure haven't."