Sam Allardyce rejected the chance to sign Romelu Lukaku while at West Ham.
Allardyce managed West Ham for four years from 2011 to 2015, earning the club promotion from the Championship and maintaining their Premier League position for three years.
The club initially thrived after his departure, with Slaven Bilic guiding the club to seventh.
The Hammers finished 11th last season and are now embroiled in a relegation battle with David Moyes at the helm.
Their struggles have caused bad blood between the supporters and the co-owners, with David Gold and David Sullivan not achieving the sort of success they predicted after buying the club in 2010.
The club have struggled to sign a proven goalscorer ever since, and Sullivan claims that Allardyce rejected the opportunity to sign Lukaku before he moved to Chelsea, then Everton and Manchester United.
“I asked Sam if he fancied Lukaku,” he told The Guardian. “Sam said he’d take him on loan but he wouldn’t buy him for £10m.
“Again I’ve supported the manager.”