From Newsday’s Christina Armario.

The son of former Mets shortstop Bud Harrelson has entered into a “cooperation agreement” to testify against a friend who allegedly slashed his sleeping stepfather to death with a samurai sword in Hauppauge.

Troy Harrelson has agreed to provide testimony, if called upon, in the upcoming trial of Zachary Gibian, who is accused of nearly beheading his stepfather, Scott Nager, 51, in February 2005 as Nager slept on his sofa.

Police say they believe Harrelson picked up Gibian at his family’s Hauppauge home shortly after the killing took place. At a pretrial hearing in March, Det. Alfred Ciccotto testified that Troy Harrelson drove his friend to a trash bin, where Gibian disposed of the murder weapon.

Jury selection in the case begins Oct. 4, Clifford said. Nager, a former New York City police officer, was sleeping on a couch when his stepson allegedly came up from behind and struck him with the sword. Nager woke up, and Gibian nearly decapitated him, prosecutors said.

Gibian’s attorney has described his client as having been taunted and threatened repeatedly by his stepfather, who kept a large collection of handguns, grenades and swords, including the murder weapon, in his home.

Bud Harrelson (above), who played with the Mets for 13 seasons and went on to manage the team, now is co-owner of the minor-league Long Island Ducks, of Central Islip. He could not be reached yesterday. Troy Harrelson’s lawyer, Paul Gianelli, did not return calls.

While this is obviously a tough time for Harrelson, at least he can rest easy knowing that his mistakes as a parent aren’t even close to the worst of any former Mets manager.