Lawyers for Bonds argued at a hearing before U.S. District Court Judge Susan Illston that the players should be excluded because of their ties to Bonds’ former trainer Greg Anderson, who is refusing to testify against the slugger.

Illston previously barred much of the evidence relating to Anderson because of his willingness to go to prison on contempt charges rather than testify at the trial set to start March 21.

Without his testimony, it could be impossible to prove that urine samples that purportedly tested positive for steroids had been collected from Bonds by Anderson.

Dressed in a dark suit and slimmed down from his San Francisco Giants playing days, Bonds sat attentively at his lawyers’ table in front of the judge during the hearing.

Illston also said she would consider on a case-by-case basis whether to exclude other evidence seized from Anderson’s home and elsewhere that prosecutors want to show the jury.

That includes a trove of documents created by Anderson that prosecutors say connect Bonds to blood and urine tests conducted at the Bay Area Laboratory Co-Operative, which was at the center of a sports doping ring broken up by federal investigators.

The judge said prosecutors could call the athletes to testify about their relationships with Anderson, who supplied many of them with steroids and whom the government claims supplied Bonds with performance-enhancing drugs.

Bonds, 46, has pleaded not guilty to 10 counts of perjury and an obstruction charge after telling a grand jury in December 2003 that he never knowingly took steroids. Bonds testified that Anderson supplied him with all kinds of substances, but he assumed they were all legal supplements.

Some players were expected to testify that Anderson supplied them with drugs and informed clients the substances were illegal steroids. Prosecutors hope the testimony will persuade jurors that Bonds had to have known that Anderson was giving him illicit performance enhancers.

"Anderson provided them with detailed instructions and explained to them these were steroids," federal prosecutor Matt Parrella told the judge.

One of Bonds’ six attorneys, Dennis Riordan, sought to bar the athletes’ testimony. He argued unsuccessfully that the government was attempting to win the case with "guilt by association."

On the prosecution witness list are Giambi and retired players Marvin Benard, Jeremy Giambi (Jason’s brother), Armando Rios, Benito Santiago, Bobby Estallela, Randy Velarde and retired football player Larry Izzo.

The judge said she may stop the parade of players from taking the witness stand if their testimony begins to sound the same.

The players’ dealings with Anderson date back a decade or more, which legal experts said could further hobble prosecutors already set back by the exclusion of the tests tied to Anderson.

"We all struggle with recalling what happened a week ago," said Vermont Law School professor Michael McCann, a sports law expert. "It happened so long ago, and these witnesses are probably going to have a difficult time recalling everything."

The judge ordered Anderson to appear in court sometime before the trial starts to reiterate his refusal to testify. Anderson will be jailed for the length of the trial, which could last a month. Anderson already served a little more than a year on contempt charged after he refused to testify before the grand jury investigating Bonds for perjury.

Anderson pleaded guilty to steroids distribution and money laundering in 2005 and served three months in prison.

"He remains resolute in his position," said Mark Geragos, Anderson’s lawyer.

Both sides will return to court Feb. 11 to wrangle over whether a secretly recorded conversation between Anderson and Bonds’ former business partner Steve Hoskins should be played for the jury.

Hoskins made the recording in front of the slugger’s locker in San Francisco in March 2003.

In that conversation, Anderson discusses how he is helping Bonds avoid infections by injecting him in different parts of his buttocks rather than in one spot.

Bonds testified before the grand jury that no one but his doctor ever injected him.