Adelaide United recruited the creaking former Brazil star against their coach's wishes, the latter revealed in a book commemorating the club's first 10 years.
Brazil legend Romario played "like a busted arse" at Adelaide United, according to former coach John Kosmina.
In an extract of 'A Decade United' published by The New Daily, Kosmina pulled no punches - slamming the signing of the then 40-year-old, who played just four Hyundai A-League games for one goal in 2006.
Kosmina also criticised the club's hierarchy at the time, claiming chairman Dario Fontanarosa, board member Mel Patzwald and Michael Petrillo - the current CEO - were all Romario's cheerleaders.
"In one of the games, I think against the New Zealand side, Romario was playing like a busted arse," the extract from Kosmina read in the book collated by journalist Loukas Founten.
"He couldn't move so I hooked him with about half-an-hour to go and when he came off he got the shits and walked straight off the pitch, grabbed his bag and left. He didn’t even have a shower.
"After that, I had to go to a meeting with Dario Fontanarosa. Michael Petrillo and Mel Patzwald were also there.
"I knew what it was all about. They told me they'd invested too much in Romario and he had to play. I told them I didn't care if he's got the shits because he was killing the team."
Kosmina continued: "I remember Dario saying, 'We don’t care about the three points, we need him to play,' and I looked at him and said, 'Are you f****** kidding?'
"They were all nice blokes but with Romario those guys were like three groupies. I was embarrassed the way they were fussing over him; it was almost sad and belittling."
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Romario's lone goal in an Adelaide shirt was still not enough to earn him praise from the disillusioned Kosmina - who also claimed the Brazilian's signing cost them the title that season, won by Melbourne Victory.
"Romario scored his goal, although Jason Spagnuolo did most of the work and basically put it in the net for him, but true to form, Romario got a toe on it to push it over the line and he achieved his ambition to score in Australia," Kosmina wrote.
"I didn't want him to finish the game, even though we were in a comfortable position, and he knew it when I took him off.
"I told him that it was nice for him to have 10 minutes on the sideline where he could stand and salute the crowd on his own without the rest of his team-mates.
"Before Romario turned up, we were playing well enough to have gone on and probably won the competition."
Romario is famously credited for scoring 1,000 goals in his career, although the record is merely anecdotal given it reportedly includes junior-level matches - with his Wikipedia page crediting him with 309 league goals for eight different clubs, and another 55 for Brazil.