Tottenham manager Harry Redknapp said his side were left with an "impossible task" after being reduced to 10 men in their 4-0 defeat by Real Madrid.
Striker Peter Crouch was sent off after 14 minutes of the Champions League quarter-final first leg following two bookings for two rash challenges.
"It was an impossible task with 10," said Redknapp. "You have to have 11 and be at your best to get a result here.
"It's not over until it's over but we've got a mountain to climb."
Spurs were left to play over 75 minutes with 10 men and were already behind to an Emmanuel Adebayor header on five minutes when Crouch was sent off.
Former Arsenal striker Adebayor went on to score again shortly after half-time before goals from Angel di Maria and Cristiano Ronaldo completed the convincing win for the Spanish side, who sit second in La Liga.
Tottenham suffered a nightmare start to the game, having to make a change to their starting XI minutes before kick-off, with Jermaine Jenas coming in after Aaron Lennon complained of feeling unwell.
Redknapp lamented: "We lost Aaron Lennon a minute before kick-off, he didn't feel well, just said he had no energy, no strength. We had to change the team just as we were leaving the dressing room.
"Then we went a goal down and got Crouchy sent off."
Crouch picked up his first caution in the eighth minute for a foul on Sergio Ramos and then six minutes later he was dismissed following a late challenge on Marcelo near the Madrid box.
Redknapp said of the England striker's dismissal: "He's certainly not one for getting red cards, but I've not seen it. I haven't spoken to Crouchy to be honest, I'm disappointed obviously, it's all we needed to go down to 10 men so early in the game."
"It was one of those days where anything that could have gone wrong did go wrong."
Crouch refused to speak after the game at the Bernabeu, but Tottenham skipper Michael Dawson revealed the striker had apologised to his team-mates.
"He [Crouch] was gutted," said Dawson. "He apologised to the lads but we went out there to give our all and it didn't go to plan.
"I didn't see the bookings so I don't know if they were harsh. To have it happen so early on when you are playing a team like Real Madrid was disappointing."
The loss means the Londoners need to create a huge upset to avoid going out of the competition in the second leg at White Hart Lane but while Redknapp knows the odds are stacked against them, he refused to concede the tie is over.
"Well, it's going to be very difficult. It certainly couldn't be much more difficult than being 4-0 down to Real Madrid but we're at home, we'll give it a go," added Redknapp.
Spurs winger Gareth Bale insists the North London club can overturn the 4-0 deficit at White Hart Lane on 13 April and reach the semi-finals.
"We have to play at our best, stop their best players and score goals at White Hart Lane. It's going to be a difficult task, everyone knows that, but I still think it's possible," the 21-year-old said.
"We are not going to sit back and take another beating from them in the second leg. Hopefully we will win and hopefully that win will be enough.
"Anything can happen. We will be ready for them."
After struggling in the opening stages, Tottenham looked to have played their way back into the game, keeping the score down to 1-0 down as they went in at half-time.
But after the break, the nine-time European champions were dominant and exploited their numerical advantage to the full.
"To get to half-time like we did, I thought we could hang in there and would have a chance but then our legs ran out a bit," Redknapp explained.
Tottenham captain Michael Dawson echoed his manager's comments.
"After going down to 10 men early on it was so difficult," he said. "We defended well after giving the early goal away, we got blocks in.
"To give another goal away was disappointing and then they scored two top-class goals.
"The White Hart Lane faithful will be there next Wednesday and we've got to go out and give it our all."