Ex-Raiders Star Barret Robbins Dead at 52

12:00 PM PT -- The Raiders released a statement on Barret Robbins' death on Friday, saying they are heartbroken over his passing.

"He played in 121 career games with 105 starts, all with the Silver and Black," the Raiders said.

"The thoughts and condolences of the entire Raider Nation are with Barret's family and friends during this difficult time."

10:00 AM PT -- Tim Brown tells us Barret had been dealing with health problems for decades ... dating back to a 2005 incident involving police.

Former Raiders All-Pro center Barret Robbins has passed away, according to his teammate Tim Brown, who says he was told the former lineman died in his sleep.

He was 52.

Brown -- who played alongside Robbins from 1998 to 2003 -- revealed the heartbreaking news Thursday night, revealing he got a call from Marissa Robbins, who told him Barrett died overnight.

"Thankfully, he passed peacefully in his sleep," Brown said.

"Please pray for their girls, his family, and tons of teammates who will be affected by this!"

Brown also referenced the incident with Robbins the day before Super Bowl XXXVII ... when Barrett went missing the day before Super Sunday, after reportedly not taking his depression medication. He resurfaced later in the night, but was disoriented.

He was suspended for the SB as then-coach Bill Callahan said he was not fit to play.

"It's unfortunate that his life was never the same after he was not allowed to play in the Super Bowl!" Brown said.

"Rest Peacefully BR, you deserve it!"

Robbins began his football career at TCU ... and was later selected by the Raiders in the 2nd round of the 1995 NFL Draft.

Barret played for nine seasons in the NFL ... with his best year coming in 2002, when he made the Pro Bowl, and was named a 1st team All-Pro.