Stressed: West Ham manager Slaven Bilic
The Hammers have struggled in their much-publicised bid to land a marquee striker signing this summer befitting the new 60,000 seater Olympic Stadium they now call home.
Slaven Bilic was forced to pay over the odds for striker Andre Ayew in a club record £20.5 million deal last week and in typical West Ham fashion he was promptly injure half an hour into his debut in the season-opening defeat to Chelsea at Stamford Bridge.
While the club were not putting a timescale on the "significant" thigh injury last night, Sullivan's teenage son Jack confirmed on Twitter Ayew will be out for four months.
Big expectations: Jonathan Calleri
Loan ranger softens Ayew blow
The blow has been softened by the arrival of young Argentinian forward Jonathan Calleri this week, though.
He will give Bilic a different option in attack but co-owner Sullivan has heaped pressure on the new loan signing straight away by revealing his rather lofty expectations for the former Boca Juniors star on the club's official website.
West Ham co-owner David Sullivan
"He's a top player and was the leading goalscorer this season in the Copa Libertadores, the South American version of the Champions League," Sullivan told whufc.com.
“He is the immediate back up for Argentina who are the number one rated team in the world.
“We expect him to be one of our top goalscorers this season.”
Calleri in action for Argentina at the Olympics
Straight in at the deep end?
Calleri could be thrown straight in at the deep end too having flown out to Romania with the rest of the Hammers squad to face champions Astra Giurgiu in the Europa League on Thursday night.
Astra knocked Bilic's side out of the competition at the third round stage last year.
And the stakes are ever higher this time around with the victors over two-legged fourth qualifying play-off making the Europa League group stage proper.
That is seen as crucial to West Ham's new existence as anchor tenants of one of the largest stadiums in Europe and Calleri could well find himself in the thick of the action with Bilic seriously lacking options at moment.