The pressure is on for Allardyce who publicly criticised Zarate before shipping him out on loan across London to Queens Park Rangers in January. Sunday's lacklustre 2-0 defeat to Manchester City will not have done anything to help the 60-year-old's case but it may be having the opposite effect for the former Birmingham City, Lazio and Inter Milan star.
The limp Hammers attack at the Etihad, exacerbated by the lack of either of their first choice strikers Andy Carroll or Diafra Sakho, highlighted not only the lack of strength in depth but also variety on the West Ham bench.
But should, as is looking increasingly likely, Big Sam loses his job next month it could open the door for the 28-year-old Argentinian - who recently elected to represent the Chilean national side - to finally realise his potential in East London.
Allardyce sent Zarate packing to QPR, then managed by Harry Redknapp, in January and told the press he "wasn't good enough" to play regularly at Upton Park.
Allardyce claimed that was "not true" and told BBC Sport at the time: "I base my feelings on what I consider to be the best team. It's a professional, clinical decision, not an emotional one," Allardyce said.
It looked like Big Sam was right too when Redknapp tried to send Zarate back to West Ham before he had even kicked a ball for the R’s. Premier League rules meant he had to stay and, with only four substitute appearances under his belt, Zarate is yet to score or lay on a goal for the relegation candidates.
It had all started so well for Zarate in East London after his move from Argentinian side Velez Sarsfield when he scored a sublime volley in a 3-1 win at Crystal Palace on back in August. But he was in and out of the side after that scoring just once more, away at Everton.
The skilful attacker, who has two years left on his West Ham contract, could well return to Upton Park with a second relegation on his CV should QPR drop after suffering the same fate at Birmingham City, where David Gold and Sullivan were also the owners at the time.
Zarate has 84 goals from 283 career games and many fans still feel the diminutive star is yet to be given a fair crack of the whip at West Ham. They will have to wait and see if a change of manager helps get the best out of a rejuvenated Zarate.