Valentino Rossi says he is not taking anything for granted despite his championship advantage, as MotoGP returns to action after a three-week break.
The Yamaha rider is 30 points ahead of team-mate Jorge Lorenzo with four races to go, having taken a commanding win at Misano before the break.
But the Italian says the championship is far from over and he is aware that he can't afford to relax in Portugal this weekend.
"It was great to go away for the break after winning in Misano and with a good championship lead and I have enjoyed having three weeks off, but now I am ready to return to work," said Rossi.
"We're in the final stage of the championship and we have a strong position but, as we've seen throughout this season, anything can happen and we know that the championship is far from over yet.
"The next three races are all good tracks for us and my team and I will aim to get as many points as possible each time and then we will see where we are in Valencia.
"Last year we struggled a little in Estoril but it's been a great track for me in the past, especially with Yamaha, and it's a place that usually produces good, close racing so I hope that's the case again this year. I also hope to see Casey back in good shape and recovered because the championship misses him."
Lorenzo is also eager to get back to work after the break, and he is looking forward to another great result in Estoril after winning last year's race.
"I am really excited to be coming back to race, a month is too long after the summer," said Lorenzo. "It's been strange to have such a long break but I've tried to use the time to prepare for the final races; I spent a week in Mallorca, training with my father and resting with my family and I enjoyed myself a lot.
"Now we go to Estoril, where I had one of the best moments of my life. In the past I was never strong there but last year I did an unbelievable race. This year it's a different situation; a different time of year, everyone has the same tyres and we are in the closing stages of the championship.
"My aim is to have a good weekend in order to keep the championship going. I am also happy that we will see Casey back this weekend because he brings another challenge for all of us."