Chelsea manager Thomas Tuchel said his team need a "fantastic script" to overturn a two-goal deficit against Real Madrid on Tuesday and qualify for the Champions League semi-finals.

Reigning European champions Chelsea have been destabilised by the enforced sale of the club after the British government sanctioned owner Roman Abramovich for his close links to Russian President Vladimir Putin following the invasion of Ukraine.

Chelsea's 3-1 defeat in the first leg at Stamford Bridge last week followed a surprise 4-1 home defeat to Brentford in the Premier League, although Chelsea got back on track with a 6-0 thrashing of Southampton this weekend.

"It is one of the biggest challenges to perform away at the Bernabeu," Tuchel said.

"It is even more difficult if you have to earn a certain result, if you need to win with a minimum of two goals or better or maybe a three-goal difference, that makes it almost impossible and very, very difficult but still it is worth trying.

"We need nothing else than a fantastic script if we want to overcome this," the German said.

"The task is incredibly high and the challenge is incredibly high given the circumstances of the first leg and where we play and against whom we play and at what stage we play this kind of match.

"It's always allowed to dream and it is sometimes important to imagine things and to dream about it but it will not shift the focus from the fact that we need to deliver and we need to be ready tomorrow."

Tuchel said he believed Chelsea face a "huge disadvantage" as 13-times European champions Real have been able to make five substitutions throughout their domestic season.

He said he believes that difference was one of the reasons his players failed to show the physical edge to their game in the first leg when Karim Benzema dominated the Chelsea defence to score his second hat-trick of this season's competition.

"We face a huge disadvantage in terms of physicality because Real Madrid has a whole year with five changes and we play the most demanding league, we play the most matches throughout the season and throughout 2022 so it is not always easy to play a physical game," Tuchel said.

"We are a team that needs the physicality, the sharpness, the commitment and the investment to be a special team. We could not implement that enough in the last match."

Five substitutions will be allowed in the Premier League from next season, something which was initially put in place following the return to action after the delays caused by the coronavirus pandemic.