West Ham manager Slaven Bilic believes star man Dimitri Payet is "irreplaceable" after the French international was sidelined for up to three months.
Payet, who has scored five goals in his impressive start to life in the Premier League, sustained an ankle injury after a tackle by James McCarthy in West Ham's 1-1 draw at Everton earlier this month.
Payet has hit the ground running after his summer arrival from Marseille, and the 28-year-old has been key to West Ham's early-season form. Indeed the Hammers are sixth in the table and level on points with Tottenham ahead of their derby clash.
"You don't have to be West Ham manager to say that he is very important for us," said Bilic ahead of Sunday's match at White Hart Lane.
"Payet is our best player and our most important player, especially when we have the ball.
"He is very important for us when it comes to scoring goals, assists or keeping the ball so we are going to miss him and it is a big blow for us.
"We are not going to play with 10 players but he is irreplaceable. He is one of those players who make your team better by 10, 20 or 50 per cent."
Payet will not have to go undergo surgery for the injury, but Bilic expects the France international to be sidelined for between nine to 12 weeks.
"He is a very strong character and he is going to be back stronger than before," added Bilic, who revealed Alex Song and Diafra Sakho could be in contention to feature against Spurs after injury lay-offs.
"The others have to step up and do more for us to make us feel his absence less than huge."
As in each Premier League match this weekend, the French national anthem will be played at White Hart Lane in tribute to the 129 people killed in last week's Paris terror attacks.
"We are all very sad for what happened," added Billic. "We are sorry for all the people who died and for their families, but we are very proud we can show - because the players are playing on a big stage in the Premier League - and it is a good thing we will hear La Marseillaise.
"On the contrary we are not scared. We don't feel unsafe. We feel proud through sport that we can show the people are united and together in this very difficult time."