Williams is "too far ahead" in the midfield battle at the start of the Formula 1 season, says Force India driver Sergio Perez.
Despite being one of the slower teams in the Australian Grand Prix, Force India managed to get both drivers in the points with Perez finishing seventh and Esteban Ocon scoring for the first time in F1 in 10th.
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Perez finished the race one spot behind Williams's Felipe Massa, but could not join Massa in staying on the lead lap.
In terms of performance, the team has fallen away more than any other in the off-season.
Comparing the fastest lap from each team over a race weekend, Force India has slipped from 101.552% relative to the outright pacesetter to 103.449% in Melbourne, where it was slower than all F1 teams bar McLaren and Sauber.
"I think Williams is too far ahead at the moment," said Perez.
"Toro Rosso was quicker than us, Haas was quicker than us - so to beat them on track with strategy, the team can be very happy with that.
"I think we came with more than we thought, more than the car's pace deserved.
"As a team we did a perfect weekend and I'm very pleased with that."
The heavy VJM10 has led to Perez going on a crash diet in a bid to lower the overall weight of the car and driver.
Perez reckoned he and Ocon were able to compensate for a lack of car performance in Melbourne and admitted the team needs to improve its car sooner rather than later.
"I think Melbourne is a track where a driver can make more of a difference," said Perez.
"It's very bumpy, a narrow and difficult track. So once we go to a more normal track where the car pace matters more we are going to struggle more.
"We need the upgrades as soon as possible, we need to work hard on the car.
"As we've seen in the past Force India normally doesn't have the greatest starts of season.
"This is probably my best start of a season with the team in my four years, so it's quite encouraging.
"There's still a long way to go but at the moment we are not where we finished [in Australia]."
Perez said in pre-season testing the team had identified "a lot of weaknesses" in the VJM10, and admitted after the first race some of those remained.
"We improved the car from testing, but I think the weaknesses are there," he said.
"We cannot really balance the car, so I think that's what we need to sort out."