Arsenal defender Gabriel Magalhaes will be out of action for "weeks" after picking up an injury during international duty, manager Mikel Arteta confirmed on Friday.
The Brazil centre-back has been ever-present in the Premier League in a Gunners back line that has conceded just five goals in 11 games.
But he suffered a thigh injury during Brazil's 2-0 friendly win over Senegal at the Emirates Stadium last weekend.
"Gabi unfortunately picked up an injury with the Brazilian national team and he's going to be out for weeks," Arteta said.
"We need to have another scan next Wednesday, and we'll have the timeline probably much clearer than we have at the moment.
"It's clearly a blow because he's our leader in our back line and, to me, it's never a positive thing. The good thing is that we have very good options and people have to stand up now and do the job."
Gabriel has formed a formidable central defensive partnership with William Saliba and is also a threat from set-pieces.
Piero Hincapie and Cristhian Mosquera are both in contention to deputise for Gabriel against Tottenham on Sunday but Arteta said it was not possible to find a like-for-like replacement.
"Every player brings specific qualities and Gabi's is his leadership, his presence and that love that he has to defend, and to transmit, as well, his body language to other players," said the Spaniard.
"We have to do it and we have to spread that. People will step up, we've done it in the past, many, many times, unfortunately.
"We played last year, the biggest and most prominent part of the season without him as well, and the team was able to cope with that."
Left-back Riccardo Calafiori – another pivotal player in Arsenal's defence – missed the recent international break with Italy.
"He's been carrying a few things and we had to bring him back," said Arteta. "He hasn't trained yet. Tomorrow we have another training session and we'll see how he is."
-- NIGERIA ONLY --
Martin Odegaard, Noni Madueke, Kai Havertz, Gabriel Martinelli, and Viktor Gyokeres are all longer-term absentees who did not feature for their countries during the international break.
"Tomorrow we have another training session, see how some of them are feeling, whether it's a bit too close for this game, or we feel that they can make a contribution in the game," said Arteta.
"So tomorrow we have more clarity."
Arsenal are four points clear of Manchester City at the top of the Premier League after they drew 2-2 with Sunderland earlier this month, ending a streak of eight wins in all competitions with no goals conceded.
The Gunners have an eye-catching record against Tottenham – losing just once in the league at home to their London rivals since 1993.
But Spurs travel to the Emirates boasting the best away record in the league this season – with four wins and a draw from five games.