Real Madrid earned a spirited 2-1 win at Alaves on Saturday with a scrappy late goal from defender Dani Carvajal to open up a provisional three-point gap at the top of La Liga.
Real captain Sergio Ramos put the visitors in front by heading home a Toni Kroos free kick after 52 minutes but gave away a penalty from which Lucas Perez levelled in the 65th.
Zinedine Zidane's Real side demonstrated their new-found grit to re-take the lead four minutes later. Isco pounced to head a Luka Modric cross against the post and the ball trickled across to Carvajal, who bundled it in from close range.
Alaves threw bodies forward in search of an equaliser but Real stood firm, with Alphonse Areola stopping an effort from the hosts' captain Manu Garcia in the eight minutes of added time.
"It was a tough game, a lot of fouls, a lot of challenges, in the rain and the cold," Marcelo said postmatch. "We knew it would be tough. We scored, we conceded and then we knew how to react.
"It's days like today that win you leagues. In such a tight league every game is important. You win the league at places like this."
Real provisionally lead the standings on 31 points from 14 games ahead of champions Barcelona, who visit fellow title rivals Atletico Madrid on Sunday.
"We knew we had to play football when we could," Zidane added. "I'm happy because the effort was enormous. Militao played and did well, Isco was fantastic. They're three really important points."
Alaves, who had lost only one of their previous seven home games this season and conceded only two goals on their own turf before facing Real, are 13th on 18 points.