Sporting must beat Barcelona at the Nou Camp and hope the Italians do not beat Olympiakos in Greece to finish second in the group and reach the knockout phase for the first time since the 2008-09 season.
"We're not playing for anything on a qualification level, we are first, which was our intention," Ernesto Valverde told a news conference on Monday.
"We are happy for that, but our opponents have a lot at stake, there's an obligation to win and we're playing in a competition which we like a lot.
"It's possible I might make a change (to the team) but we have to respect the competition."
Spanish media say that Valverde will likely rotate his side, but he will have little choice at the back with Samuel Umtiti injuring his hamstring against Celta Vigo on Saturday and out for eight weeks, along with Javier Mascherano.
That leaves Gerard Pique and Thomas Vermaelen as the only fit centre backs and Valverde said a signing in January may be needed to reinforce the position.
"We have time to assess if we need to sign a centre back," added Valverde. "When you get injuries there's always talk, but in principle we're happy with the centre backs we have got. We will have to see."
(Reporting by Rik Sharma; Editing by Christian Radnedge)
