Jenson Button laments it could take months before Mercedes are caught as, like many of their rivals, McLaren are "miles behind."
Nico Rosberg and Lewis Hamilton have had the better of the running at the start of this season, claiming all four race wins including three 1-2 results.
Rosberg is leading the Championship by four points over his team-mate while third-placed Fernando Alonso is a further 34 off the pace.
As for McLaren, after a double podium finish at the season-opening race in Australia the team has fallen behind.
Lapped by Hamilton at the last race in China, Button fears it could take months before Mercedes are caught.
"Yes I think so," the 2009 Champ told Autosport when asked it could take until the second half of the season.
"We're bringing updates all the time, some bigger than others, but I think for any team to find a second is a big ask over the next couple of races.
"And that's with Mercedes standing still. And they're not going to do that.
"It's going to be tough and we've got to be realistic about it.
"Some people might over-deliver and we might see in two or three races that we're able to fight them, but I think it would be very impressive for any team to achieve that."
And although Button says McLaren are "miles behind the Mercedes", the Brit expects his team will be involved in the fight for second with "five other teams."
He added: "We're not worried about later in the season. We feel we can develop faster than most teams."
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