Real Madrid scored late in the second half to beat Real Valladolid 1-0 in La Liga and take over sole possession of first place from Barcelona on Sunday.
Zinedine Zidane's side took advantage of the chance presented to them by Barcelona on Saturday after the Catalans came out on the wrong side of a 2-0 result away to Valencia.
However, the win did not come easy as the hosts made Los Blancos suffer throughout much of the game until Nacho popped up in the 78th minute to head home a Toni Kroos cross for the lead.
After the match, Zidane had high praise for the goalscorer: "Nacho is really professional, he's homegrown, he knows the place really well, he's always switched on, when he has to compete he does it well.
"Today I'm happy with his goal because he doesn't often do it. He's part of the team and we can create chances for defenders too."
Madrid captain Sergio Ramos added: "Nacho sums up the unity of this team and that any player can come in and make a difference regardless of how many minutes they have played this season. The whole squad is so happy for him.
"It's never easy to play away from home and we knew that Valladolid would play their usual system and defend very well and close us down and we had to work very hard to open them up."
Real midfielder Casemiro thought he had given Zidane's side an early lead when he headed home a free kick from Kroos but the goal was ruled out for offside after a VAR review.
Valladolid's Sergi Guardiola meanwhile netted late in the game but that was also ruled offside and Real clung on to earn a vital victory.
Real, who have not won the title since 2017, lead the standings on 46 points after 21 games while Barca are second on 43 and Sevilla third with 38.
Zidane said: "They are three important points, but that's all. We know there's a lot of league left. It will be difficult for all the teams, including us. But we're happy with the result, because it was a hard-fought game and we played a serious game.
"We were compact defensively, and when we had to play we did a lot better in the second half and we got three points at a tough ground against an opponent who made things difficult."