Disgraced gridiron great O.J. SIMPSON has basically banned his daughter SYDNEY from visiting him in prison after she gushed about life on the outside, sources say.

Now 65, "The Juice" has spent four years behind bars in Nevada, and he flipped out when sydney, 27, surprised him with a visit earlier this year, The ENQUIRER has learned.

"Sydney tries to be strong for her dad, but when she saw him looking so worn out, she broke down in tears," a family insider told The ENQUIRER.

And that didn't sit well with O.J., who's developed a way to make his time in jail bearable, the insider added.

"As long as he's locked into a prison routine, he can tolerate doing his time," explained the source.

"But seeing Sydney and hearing talk of the 'real world' brings him back to the ugly truth that he's stuck behind bars, perhaps for a very long time."

Simpson is serving nine to 33 years for armed robbery and won't be eligible for parole until 2017.

But he is also trying for a new trial and hopes to be out on bond within months.

At first, the source says O.J. was thrilled to catch up with Sydney, a college graduate who reportedly works for a catering company in Atlanta. But his temper soon flared.

"O.J. can deal with pals and business associates visiting, but when he sees someone he has an emotional connection to, he loses it," said the source.

"By the time their visit was over, O.J. ordered Sydney to stay away. And he told her to make the same thing clear to other family members. He doesn't want to think about life on the outside until he's free."