Lionel Messi says Barcelona "need to change a lot" if they are to avoid being knocked out of the Champions League by Napoli after relinquishing their LaLiga title.

Barca fell to a shock 2-1 loss to Osasuna in Thursday's clash at Camp Nou when only a win would do to prevent Real Madrid from sealing top spot for the first time in three years.

The defeat ultimately did not matter in the grand scheme of things as Karim Benzema's double earned Madrid a 2-1 win over Villarreal.

Barca exited the Copa del Rey at the quarter-final stage in February and all focus is now on next month's Champions League last-16 second leg with Napoli.

The rearranged tie will either be played on neutral soil in Portugal or at Camp Nou and is finely poised at 1-1 after Antoine Griezmann cancelled out Dries Mertens' opener in the first leg five months ago.

And Messi, who was on target in the defeat to Osasuna, fears Barca will exit the competition at the first knockout stage hurdle unless his team-mates show more fighting spirit.

"People are losing patience after defeats to Roma and Liverpool in recent years," he told Movistar. 

"We need a break and forget about this if we want to fight for the Champions League. We need to change a lot, otherwise we will also lose against Napoli. 

"I already said before that playing like this we won't be able to fight for the Champions League and you see, we could not even fight for the league. We need to be self-critical."