Barcelona star Lionel Messi empathised with Zinedine Zidane's high-pressure situation at Real Madrid but said top players and coaches must be ready for intense scrutiny.

Messi will be the centre of attention when his Barca side host bitter rivals Madrid in a crucial Clasico at Camp Nou on Wednesday.

Goal difference is all that separates the teams and an away victory would place Zidane's men in a strong position to win LaLiga for the first time since the 2016-17 season.

Edging three points clear would additionally be a big boost for the Frenchman, who has faced difficulties since returning for a second stint in charge of the capital club.

Barca captain Messi claimed the fact any criticism had been aimed at Zidane was evidence of the extreme pressures placed on those at the top level of the game.

"It's surprising, but those of us who have been in this for a long time, and even more at big clubs, know that this is normal," Messi told Marca.

"People forget very quickly what happened and was achieved in the past and [demand] you deliver day by day.

"Zidane surely knew when he returned that the three Champions League trophies he had won no longer mattered and [the fans] were going to demand the same as they did on his first day.

"Coaches and players of the great teams know that we are continuously in the spotlight and living with this."

Barca are undefeated in six LaLiga games against Madrid and Messi expects to face a circumspect opponent in the first Clasico of the season.

"When we play at the Bernabeu, many more spaces are generated," he said. "They come at us more because they have the obligation [to attack] being the home team and people push them for that.

"At Camp Nou they play another type of match, sitting a little further back, being closer together and going on the counter because they have very fast players in attack.

"At the Bernabeu we play 90 minutes equally. Here, the game becomes more compact and more complicated."