Carlo Ancelotti said next weekend's Clásico will be "almost" decisive in the LaLiga title race after Real Madrid beat Celta Vigo 3-2 on Sunday to ensure they go into the clash four points behind Barcelona.

Kylian Mbappé scored twice -- after Arda Güler had put Madrid ahead -- as the home side cruised to a 3-0 lead at the Bernabéu, before Celta pulled two goals back, making for an anxious final 15 minutes.

If Madrid were to beat Barcelona -- who've won all three Clásicos so far this season -- at Montjuïc, they would trail the leaders by just one point with three games remaining.

"Yes, obviously," Ancelotti said at a postmatch news conference when asked whether Madrid needed to beat Barça to stand a chance of winning the league. "I won't say Sunday's game will be decisive, but almost. ... If we win, we're a point behind. The league would still be in Barcelona's hands, but we'll have more of a chance."

Barcelona won 4-0 at the Bernabéu in the two teams' first Clásico meeting this season, and then 5-2 in the Spanish Supercopa final, before winning 3-2 after extra time in last weekend's Copa del Rey final.

"We played them last week and it was competitive," Ancelotti said. "We were close to winning. We have to play a serious game, and we'll play with all the confidence in the world."

Ancelotti praised playmaker Güler after his impressive display against Celta -- providing a goal, his second in two league games, and an assist -- and said he's in contention to start against Barça.

"The Güler of September isn't the Güler of today," Ancelotti said when asked about the player's development. "He's changed, his physical profile has changed. ... He's done better this year, and he'll do better in the coming years. He has the profile to be a first-team player at Real Madrid.

"Two months ago I had a go at the people around him [for being impatient], and now I have to congratulate them, because he's doing a good job."