Barcelona edged Athletic Club 1-0 in La Liga on Saturday night thanks to a moment of brilliance from Lamine Yamal, whose decisive goal secured three crucial points. The win restored Barca's four-point lead at the top of the table and maintained their strong domestic momentum under coach Hansi Flick.
Lopez admitted the result was vital, especially after rivals Real Madrid had won earlier in the weekend.
"We know we must maintain this advantage, and knowing Real Madrid won yesterday, it was crucial to get the win today," Lopez said.
"We did exactly that and we are thrilled. Now our focus turns to Tuesday."
The young midfielder expects a very different challenge when Barcelona travel to St James' Park for the Champions League Round of 16 first leg.
"We head into it in good spirits after the win," he explained.
"We also know we will face a similar match to the one here, in a very difficult stadium against a very physical opponent. We hope to put in a great performance, play our normal game and win."
Newcastle approach the tie looking to respond after suffering a 3-1 FA Cup defeat to Manchester City, coached by Pep Guardiola.
Barcelona and Newcastle previously met earlier this season in the Champions League league phase, where the Spanish side claimed a 2-1 victory at St James' Park - a result that could provide a psychological edge.
Champions League Schedule
First Leg: 10 March - St James' Park
Second Leg: 18 March - Spotify Camp Nou
Barcelona qualified automatically for the Round of 16 after finishing fifth in the league phase standings. Newcastle booked their place by defeating Qarabag in the knockout play-off round.
The winner of the tie will face either Atletico Madrid or Tottenham Hotspur in the quarter-finals, adding further incentive for both sides.
Pep Guardiola has insisted mentality and personality would define Manchester City's season run-in after his side powered into the FA Cup quarter-finals with an impressive 3-1 win over Newcastle United.
Manuel Neuer will miss FC Bayern Munich's crucial UEFA Champions League last-16 first-leg clash against Atalanta on Tuesday after suffering yet another calf injury, dealing a major setback to Vincent Kompany's side at a decisive stage of the season.
Marco Silva has admitted Fulham endured a "very bad afternoon" after their shock FA Cup exit against Southampton on Sunday, but insisted team selection alone did not explain the defeat.
Ryan Gravenberch has committed his long-term future to Liverpool after signing a new contract that will keep him at Anfield until the end of the 2031/32 season.
