Cesar Azpilicueta said on Monday Spain can draw inspiration from Chelsea's triumph in the Champions League after a slow start has left them struggling to make the last 16 at Euro 2020.
Azpilicueta lifted Chelsea's second European Cup as the team changed gear under new coach Thomas Tuchel, a superb finish to the season culminating in a surprise victory over Manchester City in the final.
Spain are pinning their hopes on a similar transformation after two disappointing draws against Sweden and Poland means they need to beat Slovakia on Wednesday to guarantee qualification from Group E.
They currently sit third, a point behind Slovakia and two behind Sweden.
"It's not how you start, it's how you finish," said Azpilicueta in a press conference on Monday.
"I have seen it this year in the Champions League. Before January we weren't very good, and after that we did very well.
"A lot of people gave us up for dead last season, they thought we were out of the Champions League, out of the race for top four. People write you off but you never give up."
Despite his excellent form for Chelsea, Azpilicueta has rarely been favoured by Luis Enrique and has started on the bench for both of Spain's opening two games.
"We are all fighting for places," he said. "For now, we don't know anything about the next line-up."
Azpilicueta's experience and leadership might be a valuable addition to a youthful Spanish team, who now find themselves under pressure to make it out of what looked a straightforward group.
"We are not in the situation we expected," Azpilicueta said. "We would have liked to be more comfortable but football rarely gives you what you expect. We are alive and we depend on ourselves.
"We must be humble, self-critical and correct what we are doing wrong and also assess what we are doing well. It's a combination of the two. It's an all or nothing game so we have to approach it with the confidence that we will go through."
Luis Enrique could make changes, with Thiago Alcantara and Mikel Oyarzabal among those in contention to come in.
Captain Sergio Busquets is also expected to return after rejoining the group on Friday following his negative Covid-19 test. Busquets has not played in either of Spain's first two matches.
"He's an important player, with his experience on and off the pitch," Azpilicueta said. "He's an incredible captain and we know the dominance he can bring in midfield. We're very happy he's back."