After Kimi Raikkonen won the season opener in Australia, the Finn and his team-mate Romain Grosjean were not a factor at the front in the Malaysian Grand Prix as they finished more than half a minute adrift of race winner Sebastian Vettel.
Boullier reckons that such variations in form were what the team was expecting for the season, especially because of the complications caused by the 2013 Pirelli tyres.
"It is a prediction we had after the winter testing," said Boullier. "It is going to be very, very tight.
"I think you can expect, mainly because of the tyre management situation, a different race winner each time.
"But we can say we are definitely in the top four. Ferrari, McLaren, Red Bull and us are very, very close."
Boullier thinks that the difficulties Raikkonen and Grosjean had in extracting speed from the car in wet conditions - allied to time lost working their way back up the order – were the main factors behind its failure to finish on the podium at Sepang.
"First it was [wet] qualifying and then we did not make the best start ever," he said.
"After that, we lost a lot in the first stint compared to the leaders, especially Mercedes.
"If you then compare the race pace after that, we were not bad. We were there."
Boullier does concede, however, that perhaps Lotus' competitive advantage in Australia was exacerbated by rival teams not getting their set-ups sorted.
"In Melbourne clearly we had an advantage because again some circumstances during qualifying and Friday practice did not help some teams to get their set-up ready," he said.
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