An injury-hit Real, missing key performers including top scorer Cristiano Ronaldo, Wales winger Gareth Bale and midfielder Angel Di Maria, slipped to a 2-0 defeat at mid-table Celta Vigo on Sunday that ended their chances of pipping Atletico or Barcelona to the title.
Their level has dropped considerably since they crushed Bayern Munich 5-0 on aggregate to secure their place in the final of Europe's elite club competition and Ramos said some self-criticism was urgently needed.
"After a great season in this competition the team wasn't up to scratch and we've let the Liga slip away from us in a very poor way," the Spain international told reporters.
"We can't complain or let our heads go down. We have to switch gears from the last few matches," he added.
"Now it's time to think about the Champions League final and be self-critical. We have time to reflect and talk to each other. This can't happen in the final because we'll lose," he said.
Ramos said Real's defeat at Celta and draws for Atletico and Barca showed the Spanish top flight was the strongest in the world, where any team was capable of upsetting the leaders.
"You realise that the Spanish Liga is the best in the world because any team can beat you," he said.
"Nobody would have expected Barcelona and Atletico not to win. You go home feeling sad and disappointed for having let this unique opportunity to win the title pass us by," he added.
Real will be chasing a record-extending 10th European title and their first since 2002 when they play Atletico in the Lisbon final.


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