Tottenham captain Hugo Lloris and defender Toby Alderweireld will both miss Sunday's game at home to Crystal Palace through injury.
Mauricio Pochettino said the pair will undergo scans on Friday, with the club set to learn whether either have a chance of being fit for the north London derby against Arsenal later this month.
Alderweireld suffered a hamstring strain and Lloris a groin injury during Spurs' 3-1 win over Real Madrid on Wednesday and they now face a race against time to line up against the Gunners on November 18.
"They are now going to do a scan this afternoon, tomorrow we'll have a better idea," Pochettino said.
"We can guess but we must wait for information after scan and assessment from the doctor."
Eric Dier is likely to drop into the back three against Palace while Michel Vorm will replace Lloris in goal as Tottenham look to maintain momentum following their sensational win over Madrid.
Despite their success in the Champions League, however, Spurs still trail Manchester City by eight points in the Premier League and Pochettino insists there is no room for complacency this weekend.
"We finished the game against Real Madrid and we were sitting with coaching staff in the manager's room," Pochettino said.
"We knew it was a fantastic victory but we started planning the next game and not only the next game but the game against Arsenal. For us it's so important to reduce the gap.
"The game against United was very painful - to lose the way we lost. Now, after that victory against Real Madrid, it's to be focused on the game against Crystal Palace. It has the same value as the Real Madrid game."
Tottenham can also rely on at least two of their rivals dropping points on Sunday as City host Arsenal and Manchester United travel to Chelsea.
"Manchester City are doing very well. In the Premier League and Champions League they're showing unbelievable performance. They're the most in-form team in Europe today," Pochettino said.
"But of course, it's a long way (to go). the challenge is to keep their form and maintain for the whole season."
Pochettino said Harry Kane reported no ill-effects from the game against Madrid after he missed last weekend's loss to United with a hamstring injury but Erik Lamela and Victor Wanyama remain unavailable.
Lamela has been training with the first team for a few weeks but the winger is still not ready to return following his year-long absence due to a problem with his hips.
"His problem is not mental, his problem was and is real." Pochettino said. "For Sunday it's too difficult but maybe after international break, he can be available again."
Wanyama has been out since August with a knee injury and Pochettino could not confirm the midfielder would play again before the end of the year.