Mauricio Pellegrino briefly donned the shirts of both Liverpool and Barcelona during his 16-year playing career - but it's his exploits in management that provide the most recent relevance with his former clubs.

The Argentinian is currently the man in charge at CD Leganes in Spain. Back in September, just a matter of months after taking the job, he guided the La Liga side to a shock 2-1 victory over Barcelona.

Meanwhile, he spent last season in the Premier League at Southampton, facing Jürgen Klopp's Liverpool twice and falling to defeat on both occasions.

So, there's an obvious question that springs to mind prior to the first leg of the Champions League semi-final between the Reds and the Blaugrana: Which opposing frontline kept him up at night the most?

"Not too many teams in the world have got the many talents of Liverpool and Barcelona. I cannot chose one of them, I cannot!" Pellegrino tells

"Lionel Messi and Luis Suarez, for example, are players that in one action can kill the game. Liverpool have got Mohamed Salah, Roberto Firmino or Sadio Mane - and it's the same! It's difficult to analyse the match."

The last-four tie gets underway at Camp Nou on Wednesday evening.

Barcelona head into it having secured the league title with three matches to spare after a 1-0 victory over Levante at the weekend.

And locally, the build-up to the Liverpool meeting involves stressing the need for Ernesto Valverde's side to be successful in front of their own supporters once again.

Pellegrino, of course, is familiar with the mystique of Liverpool and European competitions.

The former central defender became a Red midway through the Champions League-winning 2004-05 season, making 13 appearances. He would then return to the club in 2008 as part of Rafael Benitez's coaching staff.

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"The perception right now is that Barcelona has to do their job here," Pellegrino, speaking over the telephone from Leganes, a city on the outskirts of Madrid, says.

"The people know that Liverpool at home, in Anfield, is really strong. This is the perception of the people in general.

"Barcelona usually play in the same way in both [legs] but Liverpool maybe play in another level in Anfield."

With a trip to Sevilla on Friday to prepare for, Pellegrino will be forced to watch the Camp Nou encounter on the television.

Regardless, the tactical battles that will arise during a match between two of the best teams in Europe at this moment are ones that should excite him and other coaches greatly.

"It's really difficult to predict the result right now. When both sides are really good, the small details will determine the result," he outlines.

"I imagine that Liverpool usually like to be really aggressive in the high pressure. But it's something that Barcelona is really good at - trying to attract the teams by moving the ball in their own pitch.

"Liverpool have to be patient, don't go too high too much because they are really good [when they] break the first line.

"[Marc-Andre] Ter Stegen is really good, [Gerard] Pique, [Clement] Lenglet, Jordi Alba, [Sergi] Roberto, [Nelson] Semedo, they are players who have played for many, many years in the same way and they don't have the fear to take a risk.

"But at the same time, when they [Liverpool] regain high, they have got the chance to score.

"For me, it will be fun to see if Liverpool are able to recover the game in the opposite half and if Barcelona are able to break the first pressure of Liverpool."

On the matter of who will emerge victors to reach the Madrid final, Pellegrino's answer is similar to the question posed at the start of the interview.

"The game is 50-50," he concludes. "Because both teams are really good with different profile of players, different styles.

"Both the teams have got the same chance now."