A man who once played for the Boston Celtics is on trial in Chicago’s federal courthouse this week, accused of buying 30 Ruger firearms stolen from a South Side rail yard in April 2015.

The feds say Nate Driggers was a fence who bought the guns from thieves who helped steal more than 100 of the weapons from a parked freight train bound for Spokane, Washington. Driggers, a convicted felon, is charged with illegal possession of the guns.

Driggers’ lawyers say he is not guilty. His trial got underway Monday afternoon at the Dirksen Federal Courthouse. It is the first trial to result from a theft that authorities say flooded Chicago’s streets with stolen guns. The feds say two robbery crews banded together to steal the new weapons — worth more than $50,000 combined — divvied them up at a stash house and tried to sell them.

Authorities have since tied at least one of the stolen guns to a shooting in Chicago on Jan. 22, 2016.

Assistant U.S. Attorney Christopher Parente said Marcel “Soup” Turner, Terry “Tito” Walker and Frederick “Macboney” Lewis took their share of about 30 guns to Driggers, who bought them at his unmarked “store” — where the feds allegedly found one of the stolen Ruger firearms along with other merchandise lifted off freight trains.

Turner pleaded guilty in September and took the stand Monday afternoon as the prosecutors’ first witness. But that was after Driggers’ attorney, William Murphy, spent most of his opening statement attacking Turner’s credibility. Murphy called Turner a “career criminal” and a “thief.” He also said Driggers did not have “exclusive” control of the store where the gun was found.

Parente told the jury that cell phone data would corroborate Turner’s testimony, but Murphy said that data “doesn’t prove anything.”

Walker and Lewis have also entered guilty pleas, records show.

Driggers, a Corliss High School standout, played 15 games for the Boston Celtics in the 1996-97 season. He was found guilty in August 2009 of misdemeanor unauthorized use of a trademark involving the sale of counterfeit gym shoes. He received a fine and 12 months conditional release, records show. He also received a four-year prison sentence for a drug charge in November 2001, according to court records.