Barcelona may travel to Rome with a 4-1 advantage from the first leg, but the Ernesto Valverde insisted that his side must remain alert to the possibility of a comeback.
Own goals from Daniele De Rossi and Kostas Manolas as well as strikes from Gerard Pique and Luis Suarez have put the Catalans in a commanding position.
“I’ve been doing this long enough to know that extraordinary things can happen in a game,” Valverde said when asked if Roma could overturn the result.
“History says that, at our level, it’s hard to score against us, but we can’t think that they don’t have a chance or they won’t try.
“A mistake, an excess of confidence, they could cost us dearly and we are at the doors of the semi-finals.”