Guardiola concerned about complacency
The La Liga leaders moved a step closer to retaining their title on the weekend when they won at Villarreal and rivals Real Madrid slipped up at home to Sporting Gijon, to leave the Catalans eight points clear at the top with eight games left.
Guardiola's side are on course for a treble as they lead La Liga, have a King's Cup final in two weeks' time and are one of the favourites in Europe's elite club competition.
"There isn´t much talk about Shakhtar and they say the league is won," Guardiola told a news conference ahead of the first leg at the Nou Camp.
"The sensations I have aren´t good."
The Ukrainians, who are in the quarter-finals for the first time, had one of the best records in the group stage.
They ran Barca close in the European Super Cup in 2009 and stole a 3-2 win at the Nou Camp the last time they met in the Champions League group stages late in 2008.
"We have to play a good game or the tie will get complicated," Guardiola added.
"I've told the players we have to be focused because it would be dangerous to have to settle the tie over there.
"They are a great team, a super team that is very aggressive. They defend very well and they work like animals. They finished above Arsenal in their group."
Shakhtar coach Mircea Lucescu told an earlier news conference he believed the current Barca side were "the best team in the history of football" but noted that his club had developed rapidly in recent seasons.
"Shakhtar is the team that has progressed the most," the Romanian said.
"We won the UEFA Cup a few years ago (2009) against a great club like Werder Bremen and now we are trying to consolidate in the Champions League," he added.