The victory book their place in the last eight and beating a fellow top-six club was an important statement, according to Alderweireld.

"I think we really worked hard for the result," the central defender said. "Second half was very good. Of course, we have an unbelievable team but we have a lot of games this week, so we played with another team.

"But we showed we have a big squad and we had to grind out the result. Okay we didn't win the competition but this is a big step.

"We'll take it game by game but for the morale it's very big to win this type of game."

Jose Mourinho gave his side no chance of winning before the game given their hectic run of fixtures, where they play four times in eight days.

But they came through unscathed, even though Alderweireld believes such a schedule puts the players at risk.

"We don't want to complain, but of course it's not easy to play every 48 hours," he said. "It demands a lot from the body, even a little risk.

"But everyone works so hard for it. Today, especially second half we worked so much better, we pressed them and we could have won it. When you get the penalties it's always a bit lucky and today we were on the good side.

"The only thing that compares is (the) Christmas (schedule). This is very tough and again a little bit risky for injuries.

"It's not only tough in your mind but also your muscles. You're playing one of the biggest teams at a Premier League tempo, so it demands a lot on the body. We try to get through it in the best way possible."

Timo Werner's first Chelsea goal put Lampard's side ahead before Erik Lamela's late leveller sent it to penalties, where Mason Mount missed the decisive 10th kick.

Lampard said: "Mason will have many more nights for this club and for his country where he will play in games with huge importance on them and he will be the deciding factor on a positive note in them.

"He has my support for all times and the team and everybody around it. You miss a penalty, it is a collective when you get to a game like this."