Barca hold a comfortable 5-1 quarter-final, first-leg advantage that has them on the brink of the last four of the Champions League, but their coach is desperate to avoid any sense of relaxation among his players.
The Ukrainians caused Barca plenty of problems in the opening minutes at the Nou Camp last week when the pace of their forwards clearly unsettled the hosts' defence.
"Although we are defending a good result it will be tremendously difficult," striker Pedro told a news conference on Sunday.
"There are 90 minutes and anything can happen. They have a great team. In the King's Cup we saw what happened against Real Betis (Barca won 5-0 at home and then lost 3-1 away).
"We won't change our style. We'll go there to attack and to score goals."
Maintaining their winning momentum will be important because on their return they face a potential La Liga title decider away to Real Madrid at the Bernabeu on Saturday.
Guardiola described this clash as "a unique opportunity to strike a decisive blow," after his side came back to beat lowly Almeria 3-1 at home on Saturday.
They top the standings by eight points with seven games left to play.
REAL IN SEMIS
Four days after the 'clasico', they face Real Madrid again in the King's Cup final, and assuming Jose Mourinho's men suffer no slip ups away to Tottenham Hotspur on Wednesday, the Spanish giants are likely to meet again in the Champions League semis.
Barca travel without the injured Carles Puyol, Eric Abidal and Bojan Krkic while Andres Iniesta is suspended.
Shakhtar suffered their first defeat at the new Dondass Arena on Saturday, when they fell 1-0 to FC Obolon.
Matters were made worse by a thigh injury to Croatian defender and team captain Dario Srna, who has been ruled out for two weeks, which leaves coach Mircea Lucescu with problems at the back.
Srna joins Olexandr Kucher and former Barca defender Dmytro Chygrynskiy on the injury list while Razvan Rat is suspended.
Lucescu may have to turn to the inexperienced Serhiy Kryvtsov to play in the centre of defence with Mykola Ishchenko, Vyacheslav Shevchuk or Vasyl Kobin, who are all short of match fitness.
Probable teams:
Shakhtar Donetsk: 30-Andriy Pyatov; 32-Mykola Ishchenko, 38-Serhiy Kryvtsov, 44-Yaroslav Rakitskiy, 13-Vyacheslav Shevchuk; 3-Tomas Hubschman; 20-Douglas Costa, 8-Jadson, 10-Willian; 22-Henrik Mkhitaryan, 9-Luiz Adriano
Barcelona: 1-Victor Valdes; 2-Daniel Alves, 3-Gerard Pique, 16-Sergio Busquets, 21-Adriano Correia; 14-Javier Mascherano, 6-Xavi, 15-Seydou Keita; 17-Pedro, 10-Lionel Messi, 7-David Villa.
