At a time when Major League Baseball would like fans to focus on the All-Star Game and tight pennant races, the game will instead be drawn into its sordid past as Roger Clemens, the most decorated pitcher in history, is tried on charges he lied about taking performance-enhancing drugs.

Clemens’s trial, which begins with jury selection Wednesday in a courtroom blocks from the U.S. Capitol, will be the second recent prosecution of a former major league star accused of lying about taking banned performance-enhancing substances during his career.

Clemens, 48, is accused of committing perjury and related offenses in 2008 when he denied taking steroids and human growth hormone in testimony before a congressional committee. A conviction is hardly assured, but the trial — with a cast of larger-than-life figures who have fallen from grace — may offer legal drama worthy of Shakespeare.

The central figure is Clemens, a living legend who won an unprecedented seven Cy Young awards during his 23-year career with the Boston Red Sox, Toronto Blue Jays, New York Yankees and Houston Astros.

“What if arguably the greatest pitcher of the last half-century does jail time?” said Bob Costas, an NBC and MLB Network host. “That would reverberate for a while.”

Once destined for the Hall of Fame, Clemens faces serious prison time if convicted of perjury, obstruction of Congress and making false statements during a trial expected to last at least a month.

Clemens’s chief accuser is his one-time friend and trainer, Brian McNamee, a man with credibility problems that are certain to be highlighted by Clemens’s legal team.

Jose Canseco, a former slugger who detailed his own steroid abuse in a 2005 book, “Juiced,” could testify. So may former Yankee Chuck Knoblauch, who has admitted his own use of performance-enhancing drugs.

Andy Pettitte, a three-time American League all-star and former Clemens teammate, is almost guaranteed to take the stand. He has admitted using HGH during his career and is expected to testify that Clemens had confided in him that he had also done so.

In recent days, prosecutors have filed court papers indicating they plan to introduce evidence including syringes used by McNamee to inject Clemens and DNA analysis linking the pitcher to the needles, which were kept by the trainer in a beer can and an express shipping box.

Still, former federal prosecutors say such evidence doesn’t necessarily ensure an ironclad case, especially since perjury is one of the most difficult charges to prove at trial.

“This case is hardly a slam dunk,” said Andrew White, a former federal prosecutor and criminal defense lawyer who has handled such cases, pointing to the high-profile trial of former baseball superstar Barry Bonds, which ended ambiguously in April.

Bonds, perhaps the game’s greatest slugger, went on trial for allegedly lying to a federal grand jury about his use of steroids while playing for the San Francisco Giants. The 14-time all-star was convicted of only one count, obstruction of justice, that had nothing to do with his use of performance-enhancing drugs, and the jury was hung on all other charges.

Prosecutors have not yet announced whether they will seek to retry Bonds, who faces up to 10 years in prison at sentencing, on the unresolved charges.

In Clemens’s case, prosecutors are seeking to prove that the former pitcher lied in 2008 to the House Committee on Oversight and Reform, which was investigating the prevalence of performance-enhancing drugs in the game. A report released in 2007 by former senator George J. Mitchell cited detailed allegations that Clemens used steroids and HGH during his career. Major League Baseball has prohibited the use of such drugs without a prescription since 1971 and explicitly banned steroids in 1991.

“Let me be clear,” Clemens told House members during a nationally televised hearing. “I have never taken steroids or HGH.”

McNamee also testified in blunt terms at the same hearing, saying he injected “those drugs into the body of Roger Clemens at his direction.”

Federal prosecutors began investigating the matter when they received a referral from lawmakers concerned that one of the men had lied to Congress. After a lengthy investigation, prosecutors sided with McNamee, and a grand jury indicted Clemens on charges of perjury, obstruction of Congress and making false statements to the House Committee on Oversight and Reform.

Legal experts say prosecutors may have a tough time proving that Clemens “knowingly” took steroids and didn’t simply think he was being administered vitamins or another kind of substance. A pending legal ruling by U.S. District Judge Reggie B. Walton, who is presiding over the trial, could also hamper those efforts by preventing some testimony from former teammates of Clemens that sought to bolster McNamee’s credibility.

Prosecutors will also have to prove that any alleged lies were “material” to congressional action.

The “material” standard may be the toughest hurdle for them to overcome, experts said, because it is unclear how Clemens’s statements affected the House investigation or future congressional action.

“At the end of the day, baseball is a staged game of entertainment for an audience,” said White, the former prosecutor. “It’s going to be difficult to persuade a jury that his denial is material to anything other than his own legacy.”

It won’t help, White and other former prosecutors said, that some jurors may wonder if the government has better things to do in tough economic times than prosecute a former ballplayer who may have lied to Congress.

“With the bad economy and the overseas turmoil that continues, prosecutors are also fighting the ‘who cares’ battle,” said Steven Levin, a former federal prosecutor and a criminal defense lawyer. “They have to get a jury to care about a baseball player who may have lied to Congress, which arguably should have had more pressing matters other than steroids on which to focus.”

Staff writer Dave Sheinin contributed to this report.