Barcelona boss Ernesto Valverde insists his side must show they have learned from their surprise defeat at Leganes earlier this season when they face them again at the Nou Camp.
The Madrid minnows inflicted Barcelona's first LaLiga loss of the campaign in the reverse fixture in September.
Leganes scored two quick goals just after half-time to overturn the lead given to Valverde's team by Philippe Coutinho, and Barcelona were unable to respond.
Valverde expects his players to be ready and prepared for the reverse fixture on Sunday.
— FC Barcelona (@FCBarcelona) January 19, 2019
He told the club's official website: "The game we played against Leganes earlier this season, we did not play well. It was poor.
"It was a midweek game which came round very quickly and it was the kind of game we thought we were going to win, but you need to show that on the pitch and we got caught unaware.
"They scored two quick goals in a couple of minutes, so we need to learn from things like that. It has to teach us something.
"Leganes are still playing the same type of football with a five man defence, they defend very well. They have very good tactics and they don't concede many goals at all. We will need to be careful of their crosses and they get many players forward.
"This is a game we really need to get the three points from so we can start the second half of the season with a win."
Valverde hinted that he could rest Lionel Messi, with a Copa del Rey double header with Sevilla before the end of January and with the Champions League starting up again next month.
"It's possible that he might not play one of the upcoming games," said the Barcelona boss. "We're reaching the point when we start to count down matches. We need to be stronger than ever to achieve our objectives.
"The fixture list is tough, we know this month is tough. We'll have to make some changes and look at certain situations. We need to be smart when rotating."