Serio Perez admitted that Force India simply didn't have the speed or performance it had been expecting this weekend coming into the Italian Grand Prix, despite both cars managing to finish in the points at Monza.
"We need to keep working. Definitely this weekend we were not as strong as expected," he conceded on Sunday. "We simply didn't have the pace today to have more points.
"I had quite a clean race - we really tried to maintain our pace for long, look after the tyres without any traffic," he continued.
"We tried to stop quite early - we were really optimistic for the last stint, trying to cover [Red Bull's Max] Verstappen, but it was just far too early.
"In the end we nearly lost a position to [Williams' Felipe] Massa which would have been a disaster but in the end we managed to hold the position."
With Williams scoring twice as many points as Force India this weekend, the Grove-based team has moved back in front in the constructors' championship. Perez said that he expected fourth place to keep switching back and forth over the remainder of the season.
"We've seen a couple of races where they're stronger and we're stronger, but the important thing like from today is we maximise the potential, we score as much, as many points as are available to us and that was important for us.
"Williams was quite quick [this weekend] so hopefully we can come back as strongly at Singapore and keep the challenge on them," he said. "It's a very different track, so I expect us to be quite strong there."
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