Jorge Cadete narrowly missed football's golden age. He also did not reach the career level where a week's salary replicated the man in the street's annual wage.

Still, Cadete did well enough – earning an estimated £3.2m (€4m) during a professional career that ran from 1987 for almost two decades – to be comfortable in his retirement. But a Portuguese television documentary has given a stark insight into the decline of the 45-year-old and offers a reminder of how life after football can go badly wrong.

Cadete cites two divorces and a series of bad investments for his impoverished circumstances. He is living with his parents, with state income of £155 (€189) a week diverted to the bank to pay off debt. In the documentary, a tearful Cadete spoke of the breakdown of his relationship with his 23-year-old daughter.

"I lost everything I invested," Cadete said. "I had a lot of people around me who had no responsibility. The moment you stop playing, things change. Agents forget to call you.

"You always hear players say: 'I've got lots of friends in football.' It's a lie. When you finish nobody wants to know you."

This is a man who earned 33 caps for Portugal and appeared at Euro 96. He was a hero at Sporting Lisbon between 1987 and 1995, with his scoring touch taking him to Celtic, Celta Vigo and Benfica.

In Glasgow, where Celtic were rebuilding under the late Tommy Burns after severe financial mismanagement, Cadete's star shone brightly. He was Scotland's top scorer in the 1996-97 season, despite Rangers claiming the championship.

Celta paid a reported £3.5m for Cadete's services – his Celtic departure was acrimonious – but his career, and scoring, stalled thereafter. A role in Portugal's version of Big Brother hinted at a need for cash but when Cadete made his most recent appearance in Scotland, last year, he talked hopefully of landing a coaching job at Celtic. In hindsight, he had run out of other options.

It is debatable whether a former footballer falling on hard times should be treated any differently to someone from another profession. Yet this is a high-profile case which highlights what can happen to footballers when the circus moves on.

Cadete is not the first and will not be the last to be unable to handle a life beyond playing; Paul Gascoigne is perhaps the obvious name to mention here, while the harrowing tale of the former Arsenal full-back Kenny Sansom also gives an insight into a world many fans will not think could exist when they are cheering on their heroes. As Cadete pointed out, many football friendships are false ones.

Cadete has taken to further education in a bid to make himself employable again. Television is his favoured destination; the next time he appears there, hopefully it will be in altogether more positive circumstances.