Although Nico Hulkenberg finished inside the top two in Bahrain, the Force India driver feels lap times are "not worth a lot in these days."
Hulkenberg set the pace on the opening day in Bahrain before he losing out to Kevin Magnussen on Day Two.
Posting a 1:36.445, the German was 1.535s short of the McLaren rookie's time.
"I think we are getting closer to the potential, you can already see more from Jerez what these cars can deliver but there's such a stiff learning curve that I think people will keep getting faster and faster," he told ESPNF1.
"Even yesterday [Wednesday] with my P1, I'm not cheering, we are not focusing on performance at the moment. It's the first couple of tests and these are early tests so it's about taking these things onwards.
"The lap times are not worth a lot in these days, it's all about checking systems, understanding data. It's not a lot to be at the top of the time sheets at the moment."
The German spent part of his day working on Force India's new brake-by-wire system.
"It's not too bad for us to be honest," he said. "I got the impression, at least on my two days running [in Bahrain], that we are quite on top of it.
"Sometimes you have some moments and some real lock-ups but its still early days and we are still learning, but overall not too bad at all.
"It's just another thing to learn and get to grips with, it all feels like it's new at the moment so you don't dwell on one aspect like that too much."