Perez trailed Felipe Massa on Sunday, finishing seventh but was unable to challenge the Williams driver's race pace, a state of affairs which worries Perez.
"I think Williams is too far ahead at the moment," said the Mexican.
"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."
Indeed, Force India's VJM10 is at the tail end of the field in terms of progress compared with last year's Aussie GO, with only McLaren and Sauber showing a smaller margin of lap time progress since 2016.
Perez says the team will need to improve its car or risk falling further down the ranks.
"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."