McLaren`s racing director Eric Boullier has warned any more setbacks in the Woking-based team`s pre-season testing schedule will be reflected in their performance once the campaign gets underway.
Boullier admitted McLaren have completed less than 50 percent of their targeted mileage during the first three days of testing in Jerez with the first Grand Prix of the season in Australia less than six weeks away.
The new Honda-powered MP4-30 completed the fewest laps of all the cars on show for a third consecutive day on Tuesday, despite running nearly three times as many laps as it had managed on the opening two days.
Fernando Alonso managed 32 laps early in the day before a cooling pressure problem in the power unit meant he was unable to run in the afternoon.
"Obviously with a new engine partner the less we run the more difficult it is going to be to catch up, or, lets say, the later we will be ready to compete competitively," said Boullier.
"Every time we can`t reach the targets in mileage or development we push back the date we will be able to exploit 100 percent of our car and our power unit to fight for the win."
A Grand Prix win is something McLaren hasn`t managed since the end of the 2012 season.
However, there is some solace to their testing woes as Red Bull were the only team capable of offering any resistence to Mercedes last season with three Grand Prix victories despite an even more torrid time in testing.
"It would be a good achievement if we could finish second in the championship like they did last year, but I don`t think we can make any comparisons that early," added Boullier.
"We have tried to cover as many issues as possible and it is good to see the car straight out of the box able to do some laps without any major issues. That is the most positive part of the day."
In contrast to McLaren`s woes, there has been no sign of any let up from reigning double world champions Mercedes, who have logged one lap short of 400 in the opening three days in Jerez.
Red Bull team principal Christian Horner claimed earlier in the week that Mercedes were "taking the mickey" with such a heavy load so early in the season.
And Boullier said it is up to the other contenders to close the gap rather than hoping for a drop-off in Mercedes performance.
"I think what was more frightening was that they were doing pit stop training on the first day, so that showed their confidence level is very high.
"Obviously they had such an advantage in 2014, I don`t see them failing in 2015. The hope is that everyone else can close the gap."