Ballack, captain in the absence of so many others, climbed to his feet to score confidently his second goal since returning to the team on Boxing Day, after eight months out with an ankle injury.
Grant said: "He can't be at his best after only three games. But he has been a leader all his life. He can score goals, make assists and he is important for us. Football is becoming more tactical and more physical. You need intelligent players and he is an intelligent player."
Ballack went close to a third with a swerving free-kick as he completed his first 90 minutes since his ankle operation in April.
The return to fitness of the Germany captain has been a ray of light in a bleak mid winter of injury setbacks for Grant.
Ballack said: "It was loud in the dressing room at half-time. But in the second half we played like Chelsea can play and we deserved it. We couldn't keep playing like we played in the first half. We needed a result."