The Ligue 1 champion is in pole position to book a ticket for the semifinals following the win at Parc des Princes, yet Pastore - who scored his side's third on Wednesday night - insists the club cannot afford to take next week's return lightly.
"It's an excellent result to win 3-1 against Chelsea in a really good match of football," Pastore told the official PSG website. "I am very happy to have scored that third goal, because it will be an important goal in the return leg.
"Chelsea is a great team with great players so we will have to stay focused there, because it is still a Champions League quarterfinal."
Meanwhile, that sentiment was echoed by Thiago Motta, with the midfielder expecting Chelsea to apply plenty of pressure on its own turf.
"It's an excellent result. We have played a huge match of football. In the first half, it was very difficult for us, and then in the second, we made life very difficult for them," he said.
"We have to play a very tricky return leg at Stamford Bridge now and resist the pressure from Chelsea to qualify for the semifinals."