The Deportivo La Coruna coach fails to see why the 27-year-old would be sad at Real Madrid ahead of his side's visit to the Santiago Bernabeu
Oltra takes his team to the Bernabeu with a chance of surpassing their opponents in the table, if they can take home all three points.
But the 43-year-old has admitted he does not understand Ronaldo's feelings despite Los Blancos' disappointing start to the season.
"I see their statistics, their parties, and I see no sorrow," he told AS.com.
"He did not celebrate a goal, which is sad, but I have to respect him because I don't know the reasons. If he is sad we have not noticed it in his performance."
The former Tenerife coach still feels that the Portugal international is a major threat and believes his side will have to work especially hard to nullify his threat.
"We must try to minimise our chasing, track back, do a lot of covering and support each other. We must find the right balance," he added.
The newly-promoted side have won just one of their five league matches so far, but have also only been defeated once compared to the the two losses suffered by their weekend opponents.
These respective records have given Oltra and his side confidence ahead of their trip to the capital, and he hopes they can get the better of Jose Mourinho's men.
"Going to the Bernabeu is always a challenge. Madrid have gone 18 home matches without losing and Mourinho teams are always very strong at home," he continued.
"It is certainly not the best place to go to recover after losing, but we will fight for the victory."