"Nobody tells you how bad it is," the former defensive tackle said on Showtime's "Inside the NFL." " ... any person that calls me on the telephone, [I tell them] do not go anywhere near Oakland."
Sapp, who retired after the 2007 season -- his fourth with the Raiders -- said that Lane Kiffin, fired this week by owner Al Davis, never got a fair chance in Oakland.
"He came in there with a change of mentality. The whole system," Sapp said on "Inside the NFL." "He changed how the locker room looked because it was going to take that kind of overhaul for Oakland to become the proud franchise we all knew it was."
Sapp said Oakland won't change for the better until Davis doesn't own the team anymore.
"[Davis] is the common equation," Sapp said on "Inside the NFL." "You take him out, put him at home watching film or whatever he is doing -- you have a functioning football organization. But once he comes over the top, he goes and starts moving it around.
"Al Davis knows football -- it's just '60s and '70s football. That's what it is. He's thinking that Cliff Branch is outside and [Jim] Plunkett is dropping back and you can throw it 80 yards down the field -- deep ball, deep ball, deep ball."
Sapp even said that Davis would call in plays when Sapp was playing for the Raiders.
"I remember the first two weeks I was there, we played a preseason game. Somebody came up one time and said, 'We're going deep right here, dog.' I said, how do you know? He said, 'The phone just rang.'
"All the preparation that goes into a week of work is there, the practicing that you have to put in order to do these things, sometimes [Al Davis] messed with that part of it and that's what kills you," Sapp said on "Inside the NFL."
He cited one particular example of a Raiders defensive game plan being thrown out the window at the last minute. Sapp said Davis was behind it.
"Al Davis is the total bottom line, buck stops right there," said Sapp. "I remember one time we had a defensive game plan because we were struggling against the run. We were going to get our safeties and put them up in the box and almost have a nine-man front. We practiced this thing 80 percent of the time on Wednesday and Thursday. We showed up that Friday morning, [defensive coordinator] Rob Ryan came in and he looked like someone had just shot his dog. He said he [Davis] pulled it on us ... He snatched the teeth out of our defense."