The Galicians are still looking for their first point after defeats to Malaga and Real Sociedad, but Oubina insists they knew just how difficult the step up to the top flight would be after five seasons in the Segunda.
"The start has been no more or less difficult than I imagined because it is not easy to play against sides in the Primera who don't gift you the ball," he told Marca.
"You have to go into their half to rob it and this is uncomfortable as it makes you suffer more than you realise.
"We need to be strong mentally to move forward in a season that we all knew was going to be difficult."
And Oubina sees no better time to get off the mark than when they host another side without a point to their name in Osasuna this weekend.
"I would like to win against Osasuna because we are playing at Balaidos and have the support of our people," he said.
"It would be very positive to recuperate the good feelings we had in pre-season out on the pitch."
Osasuna meanwhile will be without their skipper Patxi Punal after he was sent-off against Barcelona last weekend and banned for four games for allegedly abusing referee Muniz Fernandez.
The four-game suspension for such offences has just been introduced this season to try and cut down on dissent towards officials, but Osasuna boss Jose Luis Mendilibar believes the punishment is harsh.
He told the club's website: "I don't like that they change things from one year to the next so that two games changes to four without knowing why.
"They tell us we need to maintain our composure towards them when every time you cough they book you. And then the post-match report is written to do the most damage possible.
"They only believe themselves and, therefore, what we have to do is speak less, me being the first."
Punal's absence could mean a debut for Ghanaian international Anthony Annan, but otherwise Mendilibar is expected to stick with the side that ran Barca so close last weekend.