Barcelona coach Ernesto Valverde has warned his side that Roma have the ability to stage a comeback in their Champions League tie, despite the Spanish side's first leg advantage.

Valverde saw his side claim a 4-1 win at the Camp Nou in last week's first leg, a win that has the side in a commanding position going into Wednesday's match at the Stadio Olimpico.

But, speaking at his pre-match press conference on Monday, the former Athletic Bilbao boss was adamant that the tie is far from over - and that the Giallorossi have shown they must be respected.

"Tomorrow I'm expecting Roma to approach the game with great intensity, especially at the beginning," Valverde said.

"They will want to get the first goal to give themselves a chance at qualifying. And we need to play a great game to get through the tie and look forward.

"We have to approach the game not thinking that we have already qualified, despite the good result we got at the Camp Nou. We are ahead, yes, but we have to play as if it were still 0-0. Because anything can happen in a Champions League match."

He added: "We know we are going up against a side it is tough to score against, but who are also strong in attack and defence. We know they will play right up until the end. In the first leg Roma showed that they have great players. Being over-confident would be extremely costly for us."

The coach revealed that midfielder Sergio Busquets will be evaluated ahead of tomorrow's game - but forward Lionel Messi is expected to start, after scoring a hat-trick at the weekend.

"Every squad wants to stop the other side's best players: we have Messi and everyone tries to restrict him," Valverde added.

"In this respect Roma did well at the Camp Nou, but we know Leo is always there to do the right thing at the right time. We'll see tomorrow how he does. And then also we need to keep an eye on their best players, like [Edin] Dzeko.

"Our heads are on tomorrow's game, we aren't thinking about semi-finals. There's no over-confidence. The other side has the ability to turn the thing arounds. We have to deliver on the pitch tomorrow to qualify."