In some ways, Lance Armstrong and Thomas Weisel seemed to be separated at birth.

As the cycling legend soared, nabbing one Tour de France title after another, the legendary Silicon Valley financier was right there alongside him -- friend, protector, doting Medici behind Armstrong's sprawling empire and party host to cyclists at his home in Marin.

"This is a guy who likes to win all the time, at everything," Armstrong once wrote of his esteemed benefactor, as if he were writing about himself. "To Thom, everything's a deal. Everything's a prizefight, a contest."

Weisel's lust for a good fight may soon be severely tested. As Armstrong appears on TV Thursday evening for what Oprah Winfrey has called his confession of using performance-enhancing drugs after years of denial, Weisel will be hanging on to every word.

Weisel, the founder of Montgomery Securities, renowned for taking public Amgen and Yahoo (YHOO), has been subpoenaed by investigators looking at possible fraud against the federal government by the now-disgraced racing star's team. And with the fates of the two men so intertwined over the years, Weisel could be facing the fight of his life.

Weisel did not return calls Wednesday, and few who know him have spoken publicly.

Jim Balassone, director of the business ethics program at Santa Clara University's Markkula Center for Applied Ethics, said "it's too early to make any judgments about who knew and didn't know" about the doping.

"We have to first hear Lance's story, then they can ask Weisel and others who facilitated the racing and were part of this milieu, what part did you play? Did you ask questions? Was the doping going on apparent to you?" Balassone said. "But this thing is like an onion; once it starts to unravel, someone will get into a jam, and that person will roll over, and then we're off and running. I think Lance will be naming and blaming people."

Weisel is not named in the redacted public version of a report last October by the United States Anti-Doping Agency, which attributed the cycling team's spectacular success to systematic doping. But it did say that the cyclist benefited from "an army of enablers" who helped him obtain EPO and other blood medications, human growth hormone and steroids, then covered up his drug use. What remains to be seen is who these enablers were.

Armstrong's "confession" could well be a precursor to his cooperating with federal investigators trying to determine if he and others defrauded the government by violating a no-doping clause the team had with its sponsor, the U.S. Postal Service. Weisel, 71, is the founder, owner and chairman of San Francisco-based Tailwind Sports. That was the holding company for the USPS cycling team that Armstrong led to an unbroken string of seven victories in the Tour de France, from 1999 to 2005.

According to a report from Matt Smith and Lance Williams with the Center for Investigative Reporting, published this week in BusinessWeek, the Postal Service paid out $40 million in federal funds to sponsor the team from 1996 to 2004. Team management, which hired and paid the riders, promised in its contracts not to tolerate doping. If Armstrong now admits to doping, his entire operation could face litigation from the federal government, along with related lawsuits already filed against Tailwind.

The New York Times reported that Armstrong was in discussions with the Justice Department to possibly testify against several team officials and owners.

The banker and the cyclist, at least according to press reports and Weisel's own autobiography, seemed at times like a single unit.

Born in Minnesota, Weisel had been a champion speed skater who almost made the 1960 U.S. Olympic team. The BusinessWeek article describes how Weisel continued to compete in sports, picking up cycling when he was 42 and grabbing two world championship gold medals in 1989 as he cast his sights on racing in the Tour de France.

"Weisel often followed Armstrong in the team car," according to the article. "He partied with him, celebrated with him and displayed Armstrong's photographs and yellow jerseys in his Montgomery Street offices."

Once Armstrong has had his say with Winfrey, Weisel's life could quickly get very complicated.

"I don't know what Mr. Weisel knew or when he knew it," said Jeffrey Dorough, spokesman for Dallas-based SCA Promotions, which has been in litigation with Tailwind over $9.5 million SCA paid Armstrong for winning the French rallies. "Would I be shocked to find out that he did know what was going on with the team? Not necessarily. In any case, we'll certainly be watching the Oprah interview very attentively."

Contact Patrick May at 408-920-5689 or follow him at Twitter.com/patmaymerc.