NEW YORK (AP) _ Izzy Lang rarely fumbled the football, but opportunity was something else. In 20 years he spiraled from a barrel-thighed pro football celebrity to a limping, homeless ex-convict.

In the past three months, he has hit bottom. He has slept on a train station bench and made a single box of fried chicken last four days.

''I'm crawling ... just like a bum,'' Izzy says. His beard is shaggy. His hair is receding and graying. He's missing four of his lower teeth, the result of a jail fight.

But there are signs that the old Izzy - ''Mr. Fizz,'' the 6-foot-1, 230- pound bruiser who charmed his friends while a Philadelphia Eagles running back in the 1960s - is coming back.

He has a room. He has kept a pledge to stop cashing bad checks, a habit that got him arrested 24 times and jailed for 22 months. And he's starting to lower his sights. He wants a job, he says, ''even if it's a matter of washing a dish.''

However, in interviews with Lang's friends and family, a question posed by his last defense lawyer, Paul Wakely, recurs: ''What caused him to go down to this?''

Israel Lang was born poor 48 years ago in the Belmont Heights section of Tampa, Fla. His father was already dead, leaving his wife and nine children ''typically poor southern blacks,'' according to a brother, Alfred Lang. ''Some days my mother had to send me to my uncle's to borrow a cup of grits.''

Izzy played tackle on the high school football team and won an athletic scholarship to the University of Tennessee, where he was a linebacker. He went pro when he was chosen 18th in the NFL draft.

The Eagles made him a running back. In five years with the Eagles, Lang rushed 244 times for 872 yards and a 3.6 average.

Izzy seemed to cover most of his yards off the field. He appeared in beer commercials and the movie, ''Where's Poppa.'' He was part of a circle of black athletes close to Robert F. Kennedy during the senator's presidential campaign in 1968.

Lang married a former Miss Philadelphia and moved into a mansion with a yard so large it cost hundreds of dollars a month to maintain. When his son was born, ''I ran down the hospital floor yelling, 'I've got a boy 3/8'''

Izzy's best friend was Bob Brown, the Eagles No. 1 draft choice in 1964. He recalls Izzy's ''great deep, resonant laugh,'' and adds: ''Even though he might not have been the star running back, he was always a fun guy for everybody to be around. We were young, our legs were fresh. We had great hopes, high ideas, all the things you have in your early 20s.''

But the fun began to end in 1969, when Lang and Brown were traded to the Los Angeles Rams. Izzy ran one play that year - a one-yard gain - before his leg was injured. Afterward, ''I couldn't even go up the steps in my home,'' he says.

Life began to throw him for loss after loss. Business ventures flopped. His marriage failed. And by 1972, he was broke and dispirited.

As an athlete, he had been pampered since grade school. ''I thought I could play it forever,'' he says.

He did have one skill, however; during a stint at a New York bank he learned how to cash a check without proper credentials.

''The Rolls Royce, tailored suits, the flare of monetary stability wants to stay with you when it's not there. You go out of bounds, beyond your means,'' he says. ''I was not in charge.''

Having learned that ''sometimes the name just opens the door,'' police said he used those of players such as Lawrence Taylor, Doug Williams and Randall Cunningham. He wrote bad checks for hundreds of dollars at a time. Eventually, he was convicted at least eight times on charges such as forgery and bank fraud.

He was spending much of his time with a woman who took his name and became his common-law wife. They had two children and by the late 1970s were living in Vancouver, Canada, where Izzy worked at a ski resort.

In April 1977, Izzy's first wife was shot to death on the porch of her home. In Izzy's absence, she had built a successful career as a manager, dating and representing singer Teddy Pendergrass.

Pendergrass later said the slaying eventually ''spurred me ... that much more'' in his career. On Izzy it had the opposite affect.

''That was the critical point in his life which caused him to go off the normal beaten path,'' says his brother Alfred.

The police ''didn't care about the murder, but they were chasing me around for writing checks,'' Izzy recalls.

The change in Izzy also apparently affected his second family. Patti Lang left him in 1979 and resettled in Oakhurst, Calif., with their sons, who now are 17 and 14.

''I wouldn't want my sons to see him right now,'' Patti says. ''They realize he's just been a real jerk.''

Besides writing bad checks, ''I don't think he knew of any other way to earn,'' she adds. ''He was the person who wanted to start at the top as the bank executive, instead of working your way up.''

Finally he was sent to jail by judges in Virginia and New Jersey, and he served 22 months in jail. When he got out last October he called Alfred, whose sons still look up to their uncle. ''He has already achieved more than any other member of the family will ever achieve,'' Alfred explains.

While in prison, Izzy says, he vowed not to write any more bad checks. That vow was tested after his release when he found himself in New York and out of money. He went to Penn Station and spent several nights asleep on a bench.

He met Leonard Lawrence, another homeless man, who recalls that Izzy was sad and quiet at first. As they got to know each other, ''He began to smile. He began to laugh and then he became a pain,'' he says affectionately. ''He just needs friends.''

Izzy also met Jean Winn, housing coordinator for a non-profit organization that helps the homeless.

She recalls: ''He said: 'I screwed up some things myself and that's why I'm here.' He was very articulate and intelligent. When you meet a person who had so much and was honest about what happened to them, it makes you want to help so much more.''

Winn helped Izzy get a tiny YMCA room, where during a recent interview he apologized to a visitor. ''There were days when I could say, 'Would you like to have a cup of coffee?''

He pulled a small stack of blank checks out of a satchel, and admitted that his circumstances tempt him to use his only real skill. But then he ripped the checks into pieces and threw them in the wastepaper basket.

For a time, Lang lived in a Harlem apartment where neighbors used drugs. He recalls spending New Year's Eve successfully convincing one of them not to get high, and greeting the New Year on his knees in prayer.

For all his troubles, Izzy says he has discovered joy in small things, like ''just saying 'Hello, good morning.'''

''It's a good thing to have wealth, but you can appreciate when it's not there anymore and you have the simplest beauties of life. That's what coming down to the streets is all about,'' he says. ''You see the forest, buddy. The trees aren't there.''

END ADV for Release Tues Jan 22 and thereafter