MADRID — One by one, Real Madrid defenders started going down.

First it was captain Sergio Ramos with a muscle injury. Then Raphael Varane with the coronavirus. Next was Lucas Vázquez with a knee problem.

The outlook was grim for the Spanish powerhouse ahead of the decisive game against Liverpool in the Champions League quarterfinals on Wednesday. Madrid's depleted defense would have to go against the English club's prolific attack to try to protect a 3-1 win from last week's first leg.

It turned out there was no real reason for concern.

It was because of a solid performance by that makeshift defense that Madrid held on for a 0-0 draw at Anfield and made it back to the Champions League semifinals after a two-year absence.

As the English team created chance after chance, the Madrid defenders held strong, clearing and blocking attempt after attempt.

"The players always want more and the team always shows that character," Madrid coach Zinedine Zidane said. "When there are difficulties, they are even more united and want to step up. We have immense quality, but the key is the character of the players."

Only Ferland Mendy was a regular starter in the Madrid defense against Liverpool. Substitutes Éder Militão and Nacho Fernández played superbly in central defense, while midfielder Federico Valverde did well as a right back. And with help of an outstanding performance by goalkeeper Thibaut Courtois and some solid defending by midfielder Casemiro, Madrid kept in check the dangerous trio of Mohamed Salah, Roberto Firmino and Sadio Mané to reach the European semifinals for the ninth time in 11 seasons.

Militão and Nacho had already been key for Madrid in the first leg against Liverpool, when Ramos and Varane also weren't available.

"We are part of the squad and we are here for a reason," Nacho said. "We are well-prepared to play games like this. We have played three of the most demanding games together and we have produced top-level performances. So I'm pleased for myself, for Militão and especially for the whole team."

The duo also thrived in the Spanish league last weekend against Barcelona in the clásico, which Madrid won 2-1 to stay in position to repeat as Spanish champions.

"They showed that they are ready to play for Real Madrid," Casemiro said. "It's not easy to play for this team, but they are ready. We were missing Ramos and Varane, two of our captains, but Nacho and Militão came through and showed their worth."

In the right side of the defense, Valverde held his ground while replacing Vázquez, who had been playing well in the absence of regular starter Dani Carvajal because of a long injury layoff. Vázquez got hurt in the first half of the match against Barcelona on Saturday.

"Valverde put in a great performance in a position where he's not used to play," Zidane said.

And when Valverde and the rest of the makeshift defense failed, Courtois was there to keep Madrid safe.

"He is playing brilliantly," Zidane said. "It's so important to have a goalkeeper who is as secure as he is. He has always been like that for us. He has been doing a fantastic job."

Zidane soon is expected to get some of his regular starters in defense back, especially Varane and Carvajal, who are in the final stages of their recovery. But Vázquez is likely to miss the rest of the season and Ramos will still be out for a while because he has also tested positive for COVID-19.

Zidane is probably not as concerned now, though, knowing that he can safely count on all the defenders in his squad.