Slaven Bilic has been accused of showing a lack of respect by not taking to the bench for West Ham's opening UEFA Europa League encounter against Andorran side Lusitanos on Friday.
The English Premier League club won its first qualifying round first leg 3-0 at Upton Park thanks to Diafra Sakho's double, with academy manager Terry Westley in charge.
An experimental side included defender Reece Oxford, who became the club's youngest player, but the lack of its new manager on the touchline prompted fury from his Lusitanos counterpart, Xavi Roura, after the game.
"Bilic showed a lack of respect by not being on the bench," Roura said.
"It makes me sad, in a country where fair play was invented, that something like this could happen.
"I think he must have thought our team was not important for him to be present.
"I imagine that he has won many titles and maybe he thought he was the 'special one'.
"The minimum thing I can hope for is that with a club like West Ham, this won't happen again.
"I expected him to be on the bench. Should he be there for the second leg? He is the West Ham coach so yes, the 'special one' should come to Andorra."