File Photo: Barcelona s Brazilian forward Raphinha (L) fights for the ball with Sevilla s Argentinian defender Marcos Acuna during the Spanish league football match between FC Barcelona and Sevilla FC at the Camp Nou stadium in Barcelona. AFP
The champions are third in La Liga and trail leaders Real Madrid by eight points, with Los Blancos facing second-place Girona on Saturday.
Barcelona host Granada Sunday and will have the chance to make up ground on at least one of the top two.
Ter Stegen last played for Barcelona in November because of a back injury, with Inaki Pena filling in for him.
In that time Barcelona suffered heavy defeats by Real Madrid in the Spanish Super Cup final and were knocked out of the Copa del Rey by Athletic Bilbao.
"(Ter Stegen) is a key player for us, one of the captains and leaders of the squad," Xavi told a news conference.
"I'm very happy with Inaki, he showed he's a goalkeeper who can be trusted (but) very happy for Marc -- he's so key for us and the squad."
Xavi also said Raphinha was ready to play after a hamstring problem which has kept him out for a few weeks.
"Rapha will be available tomorrow, he's recovered well," said Xavi.
"We've seen him train and he's in the same dynamic as he was before his injury."
Xavi said the clash between Madrid and Girona was a chance for his team to keep the pressure on in the title race.
"What we need to do is win tomorrow and even more so knowing that one of the two, or both of them, will drop points," said the coach.
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