The visitors came out firing in the second half and they almost went ahead after 50 minutes when Dani Carvajal played in Karim Benzema, who saw his first-time strike saved by Andre Onana.
Marco Asensio returned to the scoresheet for Real Madrid with an important late victor against Ajax, which delighted Santiago Solari. "We are ready to fight for everything, to get to the final of the Copa del Rey and go as far as possible in the Champions League".
They were also denied a first-half opener when Nicolas Tagliafico headed home but for the first time in Champions League history, the goal was ruled out after Slovenian referee Damir Skomina checked with the VAR and Dusan Tadic was judged offside.
Rather than disallowing the goal for a foul on Courtois, who struggled to claim a header from Mattijs De Ligt under pressure, VAR ruled that the player in the Real Madrid goalkeeper's path was actually caught offside by a fraction.
Ajax had looked on course for a draw when Hakim Ziyech shot under Thibaut Courtois in the 75th minute to cancel out Karim Benzema's opener 15 minutes earlier.
Ten Hag said Real would be favourites with Ajax still short of experience at the highest level after finishing second in the group phase behind Bayern Munich. "There we can learn from Madrid - they created less chances but scored more goals". "We trust what VAR or the referees say", he said.
"I hope there will be many more and every day I get up excited to represent the team as captain". But it started confidently and Tadic almost gave Ajax the lead, his 26th-minute shot hitting the post after beating Courtois. Solari gave Vinicius 90 minutes in his first match in charge, more than Lopetegui had in all 14 of his.
Tadic then held off Sergio Ramos to fire in a shot that hit the post, and Ziyech missed another one-on-one chance with Courtois as Ajax's incisive passing stretched the visitors.
The former Chelsea keeper admitted that while it is yet to be perfected, the positives outweigh the negatives, praising its use while speaking in his press conference ahead of Madrid's last 16 first leg tie against Ajax on Wednesday.
"[Vinicius] did well, but they all did", the Argentine said.
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