Adrian Sutil fears that overtaking will not be as easy as some expect it to be during Sunday's Italian Grand Prix.
The Force India driver found it difficult to pass other cars during today's two free practice sessions, and suspects that passing will be more difficult than it was during the Belgian Grand Prix two weeks ago.
"It's difficult to overtake," said Sutil. "It's good that we have two DRS zones, but it's still hard work to pass another car because there are so many high-speed corners before the long straights, so it's not possible to follow closely. You have a bad exit and all of your advantage is lost; it's not enough at the end of the straight.
"It's not going to be impossible, but it will not be as easy as it was at Spa."
Sutil added that he was able to attempt to simulate a DRS pass by running behind other cars that did not have their rear wings open in the activation zones. But he found that even then it was tough to pass.
He added that if overtaking proves to be this difficult in the race, it would have strategic and setup implications. While running a little extra downforce could give a lap-time boost in qualifying, it could also make drivers sitting ducks to be passed during the races. But if passing is as difficult as Sutil suspects, it opens up the possibility of running some more wing without that disadvantage.
"Being in a position to pass other cars was not easy," said the German. "I knew where the DRS activation was so I pressed it at that time, but it was still not possible sometimes.
"It's still possible to hold people up here so that could be important for strategy. The DRS switch is quite big if you go to higher downforce, so it's good for qualifying but maybe not so good for the race."
Sutil admitted that he was disappointed with the performance of the car during practice and that he is hoping that the team can boost its top speed, something that could also make it easier for him to overtake during the race. He ended the day 12th fastest, 1.486sec off pacesetter Sebastian Vettel.
"We're just not as competitive as we thought," he said. "It's just a Friday so it can change tomorrow.
"We just have to make sure we are 100 percent on it in qualifying. It's a tricky one because we still need some top speed but we need to find the right compromise for the race."