Real Madrid extended their lead at the top of the table to 5 points as they ran out 3-0 winners over tenth-placed Alaves at the Santiago Bernabeu on Sunday.
The 29-year-old coverted Madrid's first true opening after good work from right-back Dani Carvajal.
Real: Casilla 7; Danilo 8, Pepe 7, Varane 6, Nacho 8; Kroos 7, Modric 7, Isco 10; Ronaldo 7, Benzema 8, Bale 7.
Isco's impressive late finish was his fifth goal in his last six league starts, boosting his chances of playing a key role as LaLiga and the Champions League are decided.
It was a great goal, though, with Cristiano Ronaldo slipping a terrific pass into the path of Isco, who lashed home into the top of the net.
"We know that at any moment we can do damage to our opponent - that is what this team has".
"April? We know that we must always improve, but playing every three days, you can't always have a flawless 90 minutes".
Madrid's victory came with Sergio Ramos, Marcelo, Keylor Navas and James Rodriguez all rested, while Casemiro was suspended. Sevilla have surrendered a nine-point lead over Atletico in the space of four games. We scored three goals, maybe it's a bit hard on them, but we kept our goal to zero and that's important.
All three fired off target from the edge of the box as Madrid started brightly, but they had to wait 31 minutes for the opener.
Alaves had another chance to find an equaliser a few minutes later when the ball fell to Edgar Mendez, but he could only send his strike wide from eight yards out.
However, Isco settled their nerves when he rocketed Ronaldo's through ball into the roof of the net from a narrow angle.
Gareth Bale's thunderous free-kick smacked against the crossbar and Nacho was on hand to head in the rebound.
Real Sociedad: Real Sociedad's hopes of finishing fourth in La Liga and earning a shot at qualifying for the Champions League are fading fast after they drew 1-1 at home to Leganes yesterday, failing to win for a third consecutive game.
The win means Madrid are now five points clear at the summit.