"It is not to underestimate the opposition but sometimes you have to make tough decisions", said Ramos after the match.
Ramos' team-mate Dani Carvajal received a two-game ban from Uefa when he was judged to have been booked on goal in the final minute of a 6-0 win over Apoel Nicosia in last season's tournament.
Football's favourite pantomime villain Sergio Ramos could be handed a big slice of karma this week, as reports have emerged claiming he could be handed a two-match ban after purposely earning himself a booking against Ajax.
Afterwards, Ramos, 32, tweeted: "I have not forced the card".
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The England captain was suspended for his country's World Cup qualifier in Azerbaijan in October 2004 after picking up his second caution of the campaign against Wales a few days earlier.
'Ajax have had their problems of late, not least a bruising 6-2 loss at Feyenoord, yet at times here they were exhilarating, ' said the Uefa website after the game.
Seven years prior to that, the tournament organizers fined Sergio Ramos and Xabi Alonso for the same, while also giving the then manager Jose Mourinho a one-game touchline ban.
But the reigning champions, seeking a fourth straight title, were given a major scare by the only team left in the competition who had to come through qualifying.
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That's similar to Washington, which allows parents to opt-out of vaccinating their children because of personal beliefs. Measles spreads through the air when an infected person coughs or sneezes, according to Vancouver Coastal Health.
UEFA has punished players in the past for similar offences.
All yellow cards and pending suspensions expire after the quarter-finals and can not be carried forward to the semis.
Three yellow cards brings a one-match suspension but Ramos may have seen sitting out the second match against Ajax as preferable to a punishment in the quarter-finals.
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However, he may also miss the first leg of a quarter-final should Real progress.