The Liga champions have already secured a berth in the next stage of the competition, but go into Wednesday's game on the back of patchy domestic form.
Barca suffered the rare setback of losing consecutive games at the beginning of December, going down defeats against Ajax in Group H and Athletic Bilbao in La Liga, before bouncing back against Cartagena in the Copa del Rey.
But Busquets, who did not play in the side that lost 2-1 to Celtic away from home last season, insists Gerardo Martino remain in confident mood.
"There are no doubts in the team," he said. "When you lose there are things that you don't do well but we have no doubts at all, about either the style of play or any player.
"In the world of football only the results are important. We have to stay outside of the criticism and keep doing the right things.
"If there had been a third defeat in a row, it would have been a long story. Everyone will have their opinion, but we have to put that to one side, we know what we have to do.
"We hope that within a few months, we are still in all the competitions fighting for the titles."
‘He instantly popped into our ratings as one of the best U21 midfielders in Europe. The impressive thing is Slot has made him into more of a no.6' Inside Ryan Gravenberch's transformation at Liverpool
‘I don’t think Liverpool would look at Ollie Watkins, a striker isn’t a pressing issue for them – it’s Arsenal who need one’ Former Reds star explains why his old club don’t need an out-and-out forward this summer
