Martino has come under fire following the defeat, which dropped the Catalans three points behind Real Madrid in the Primera Division title race.
Xavi admitted he was frustrated to be an unused substitute at Anoeta, but has come out in support of Martino - describing him as his "superior" - and suggested criticism of the Argentinian was unwarranted.
"People always look for scapegoats. The gaffer has been made to carry the can and that's not fair. We win and lose as a team," Xavi was quoted as saying in Marca.
"The coach is self-critical and that is to his credit.
"The coach is in charge. I wasn't brought up to try to go over the coach's head, whatever he has or hasn't won.
"I get upset when I'm not involved or I don't feel good on the pitch. That happens to everyone, but I respect the coach's decision. He is my superior."
Xavi is therefore ready to move forward with Barca very much alive in three competitions.
Barca can claw back lost ground in the league at the weekend, with the Madrid clubs to meet in a derby clash on the same day they host Almeria.
In the Champions League, Martino's side boast a two-goal advantage over Manchester City ahead of a home second leg, while they will play Madrid in April's Copa del Rey final.
"We are in pole position and competitive," Xavi said.
"We are going to be optimistic in the dressing room.
"But there can be no more slip-ups and we have a big opportunity to get back on track on Sunday."