McLaren managing director Jonathan Neale admits they will find it difficult to challenge for wins in the second half of the season.
The Woking squad endured a nightmare first half of the campaign with Jenson Button's fifth place in China their best finish to date.
Although the team are determined to fight until the end of the campaign, their odds of finishing on the podium at Spa continue to increase with Paddy Power, and Neale conceded during a Vodafone McLaren Mercedes phone-in that they will find it difficult to win races.
"I think that will be a real challenge if I'm honest. The areas that we're working on this car are areas that are either directly or indirectly relevant to our 2014 campaign," he said.
"Most teams by now will be switching a greater proportion of their resource, and much of the design organisation, across to next year's car. There's four months to the end of the year and a lot of work to be done to get ready for next year.
"So I think, inevitably, there will start to be an increasing focus on 2014."
If they fail to win a race in the final nine grands prix then it will be the first time since 2006 that McLaren went a whole season without a victory.
McLaren's chances of finishing in the top six at the Belgian GP are looking better at Paddy Power.
Jenson Button, though, was quite upbeat about a possible victory during the latter half of the season, but Neale isn't quite so optimistic.
"I think I'd want to underplay it a bit more than that. Jenson was - we all were - interested in the learning and understanding that we've developed over the last couple of months on the car," he said.
"We worked incredibly hard to take a package of upgrades to Hungary; we didn't get everything on the package that we were expecting, so there's still outstanding work to do and we'll continue that work over Spa and Monza.
"Spa is a fantastic circuit and the drivers are always excited to get there, but it's notoriously difficult and I think, from the weather forecasts I've seen so far, the qualifying and the race could well be wet.
"I don't think anybody would go to Spa feeling that they were confident. I think we'll struggle to be right at the front but nevertheless we are hoping to make some further gains."