Barcelona's Marc-Andre ter Stegen feels a moment of humiliation last time he played against Roma at the Stadio Olimpico might have made him a stronger goalkeeper.

Ernesto Valverde's men are in the Italian capital for the second leg of their Champions League quarter-final, boasting a 4-1 lead.

Germany international Ter Stegen impressed in that match and is indisputably Barca's number one.

That was not the case for the sides' meeting in September 2015, when he was generally selected for cup games before Claudio Bravo retook the gloves for LaLiga duty.

Alessandro Florenzi's remarkable long-range strike from on the right touchline and just inside the Barcelona half caught out Ter Stegen and helped Roma to a 1-1 group-stage draw.

"I haven't changed since that goal," he told a pre-match news conference. "These things are rare.

"Maybe the goal made me a bit stronger because of what was said about me but it certainly didn't change my game.

"Maybe I am a little more cautious of shots from the halfway line... but it's part of life, part of football.

"Things happen that you don't expect, like that great goal." 

Expecting the unexpected might be one way for Ter Stegen and his Barca team-mates to guard against complacency in a tie many expect to be a formality from this point.

"Sometimes you need a bit of luck at this stage of the Champions League to progress," he added.

"We've had good results so far this season and our game has improved every time we've been on the field. Tomorrow is another step, but it won't be easy."