Along with Luis Suarez, Messi and Neymar led a Barcelona attack which won nine trophies in three years under Luis Enrique, scoring 364 goals between them. However, Neymar took the surprise decision to move to PSG in a world record €222 million deal in August in search of "a new challenge."

As a result, new coach Ernesto Valverde has had to build a new-look Barca side, with the emphasis moving back to the defence and the midfield. Barca have subsequently conceded just six goals in their last 19 games and Messi recognises the strengths of Valverde's new system.

"Neymar's departure has led to a change in our playing style," Messi, who signed his new contract at Camp Nou on Saturday, told German magazine Kicker as part of an interview with European Sports Media.

"We've lost some attacking power but we are better organised defensively. Our midfield is playing more calmly and we are better balanced. It has made us stronger defensively."

Barca are one of just three European teams to remain unbeaten in both their respective league and the Champions League campaigns this season, along with Neymar's PSG and Manchester City. Messi singled those two sides out as the Catalans' biggest threats at the moment, but wouldn't rule out Real Madrid or Bayern Munich, either.

"[Man] City have been one of the strongest teams so far this season together with PSG," the Argentina international added.

"But the season is still young; I would never discount Real Madrid because of their class and experience, even though they aren't picking up the expected results at the moment. Nor Bayern Munich -- Bayern are the other big team that will be ready come the end of the season."

More was expected of Spanish and European champions Madrid this season after they began the campaign by hammering Barca in the Spanish Super Cup.

However, a lot has changed in the three months following those two matches, with La Liga leaders Barca building an eight-point lead over Zinedine Zidane's side after 13 matches -- Valencia are four points back in second place.

"It's only temporary," Messi said of the idea that Madrid are in crisis. "It's not the first time we see a club like Real in such a situation. In the end, though, because of their squad and players, they'll be fighting for every title again. Because it's always this way."