The exiled West Ham United striker was shipped out to QPR on loan in January by Hammers boss Sam Allardyce who said the Argentina-born star "simply wasn't good enough" to get into his team, as reported by BBC Sport at the time.
Zarate has form as a disruptive influence. Allardyce's frank words had come as a response to claims from an unhappy Zarate that Big Sam refused to play him because he had been signed by West Ham chairman David Sullivan.
But reportedly being called a "bad egg" by one of football's most controversial characters marks a new low for the 28-year-old who recently switched his allegiances to Chile after being ignored by Argentina.
The skilful former Lazio and Inter Milan forward is said to be one of the intended targets of Barton's tirade after the Hoops were sent crashing down to the Championship following a 6-0 thumping from Manchester City at the weekend.
The paper also claims insiders have accused Zarate and others of putting in minimal effort in training.
And that sparked a furious outburst from Barton following their demotion from the top flight.
Barton said: "There’s a few people who need to have a good look at themselves.
"On the whole, the dressing room has turned up and given everything. One or two bad eggs have spoiled it.
"If it had been done my way, they would have been out of the building straight away.”
West Ham actually tried to bring Zarate back from his ill-fated loan at the end of January when their move for Tottenham Hotspur striker Emmanuel Adebayor fell through at the 11th hour, but were stopped in their tracks by Premier League rules.
The news will come as something of a disappointment to Hammers fans, many of whom were upset the club had let the diminutive striker go in the first place.
Zarate started life at West Ham with a bang at the beginning of the season when he scored a wonderful volley in the club's first win of the season - a 3-1 triumph at Crystal Palace.
But he was rarely used by Allardyce thereafter, with top scorer Diafra Sakho and fellow summer signing Enner Valencia forging a formidable partnership up front for the Hammers as they secured their best ever start to a Premier League campaign.
Zarate impressed in the odd cameo and fans felt he offered something different to the club's other strikers. But he would score just one more goal, in a 2-1 defeat at Everton, before being sent packing to Loftus Road where he has played only twice since.