Celtic are still a "fantastic team" and have not given up on winning a 10th successive Scottish Premiership title, captain Scott Brown says.
The skipper was among 13 players who had to isolate following Christopher Jullien's positive Covid-19 test after the club's Dubai training camp.
Depleted Celtic - also without manager Neil Lennon - drew both matches in the players' absence and trail Rangers by 21 points with three games in hand.
"We always have the faith," Brown said.
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"We've always got that positivity. We know that we can keep winning games and that's what we have to do to put pressure on our rivals.
"Yeah, I don't see why not [winning the league is still achievable]. We believe that it is, but we need to make sure we win every single game now."
Lennon, Brown and the other isolating players - except one who has also tested positive - return for Wednesday's match at Livingston as Celtic seek a first win in four outings.
"Isolation was hard, seeing the lads playing and not everyone being able to help them out," said Brown, who sidestepped questions about the club's protocols in Dubai.
The 35-year-old "can't put his finger on" why there has been such a big drop-off in standards at Celtic this season.
As well as their title deficit, Lennon's men have been knocked out of Europe twice and eliminated from the Scottish League Cup, although they did complete last season's quadruple treble with victory in the rescheduled Scottish Cup final.
"We're still there, we're still trying," Brown said. "We still believe we're a fantastic team, but we just need to make sure we keep showing it in games."
Brown has lost his place in midfield to Ivorian Ismaila Soro, who has started six of the past seven games, and the skipper added: "It is fine. Soro has done fantastic and he is a great lad.
"I have played 60 games for the last 14, 15 seasons. For me, it is about trying to help Soro out as much as I can because he is still young. I am here for the gaffer whenever he needs me."
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