Karim Benzema scored the only goal as Real Madrid moved six points clear of Barcelona at the top of La Liga thanks to a 1-0 win against rivals Atletico Madrid.
Real coach Zinedine Zidane had begun the match with a compact narrow formation containing five midfielders but after failing to break down Atletico he hauled off Toni Kroos and Isco at the start of the second half for natural wingers Lucas Vazquez and Vinicius Jr.
"I wasn't happy," Zidane said. "But it was my responsibility. I didn't like it, and I took off Isco and Toni, but I could have taken off another two. A change was needed, to open up the game. But the responsibility for the first half is mine.
"The changes changed the game. In the second half we changed our attitude, there was more intensity. We were much better in the second half. I think we deserved the victory and the three points."
Brazilian teenager Vinicius helped burst open a stubborn Atletico with some patient play in midfield, taking out three defenders by releasing Mendy who needed only one touch to pick out Benzema in the area.
Atletico rarely looked like troubling a Real defence that have only conceded 13 goals in 22 league games this season, although they had a strong penalty appeal turned down when Casemiro sent Morata to the ground in the first half.
"It was a clear penalty," Atletico coach Diego Simeone said. "We have VAR for justice and clarity, and here we had neither."
Benzema's strike gave Real their first home victory over Atletico in the league since 2012.
Barca can reduce the margin to three if they beat Levante on Sunday.
Meanwhile, Atletico are fifth and trail their local rivals by 13 points.
And their injury problems deepened when striker Alvaro Morata limped off early in the second half with a suspected muscle problem.
"He came off because he got a bad knock on his leg," Simeone said postmatch. "He didn't know if it was an injury or just a knock. He was struggling so I decided to take him off."
The defeat piled further pressure on Simeone, who has failed to win any of his last five games and is enduring his worst spell since taking charge of the club in December 2011.
Information from Reuters and ESPN FC's Alex Kirkland was used in this report.