Nick Heidfeld believes the lack of updates is the main reason why his BMW Sauber team has struggled to make an impression in the early part of the season.
The German squad started the season as one of the favorites to fight for the title after showing strong form in testing, but after three races the team has scored just four points and is already 32 behind championship leader Brawn GP.
Heidfeld reckons there has been a lack of development that has hindered his team.
"I guess we didn't have enough updates, not new parts in the first couple of races," Heidfeld told reporters in Bahrain on Thursday. "During winter testing we were quite happy with our pace. Also you never know how much fuel the others have, but you analyze the data and the lap times and we thought we were in a good position. But then I think we just lacked development."
He added: "I think in the first three races our performance got a little worse, step by step. I guess because some of the other teams brought updates which we didn't have. As we have no major changes here I don't expect a very different picture. It depends more on the others bringing updates again or not.
"But compared to what we had in China I don't expect too many differences. Before China there was talk of McLaren, Renault, a couple of teams bringing updates, so it's probably more about how the car suits the track and how well we get everything together, as the lap times in the midfield, where we are now unfortunately, are very close together."
Heidfeld admitted he fears the points gap to the leaders is becoming too big to overcome, but he remains hopeful BMW will make progress when it introduces new updates at the Spanish Grand Prix.
"I think it's going to be very difficult from Barcelona," he said. "Hopefully we will have a good car there to win back some points compared to the others. Firstly because the advantage that they have, especially Brawn but now also Red Bull, is quite big in lap times.
"So even if we make a good step it might bring us closer to them and hopefully to the front of the midfield. But obviously I don't know how it's going to be. I think it's unlikely that we just catch up with them, because they develop their cars as well.
"After here, we already have four races behind us, which is already quite a big percentage of the season behind us."