McLaren driver Jenson Button is not expecting to pick up points at this weekend's Mexico Grand Prix, in what he expects to be the toughest race of the season.
The 2009 Drivers' World Champion will take a 20-place grid penalty in Mexico City, while Spanish team-mate Fernando Alonso will be set back 15 places for a new engine and gearbox he received on his car.
Honda want both drivers to have new engines in Mexico, with the Brit expected to have two across the race weekend, meaning a combined 20-place grid penalty.
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McLaren's engine supplier have struggled since returning to the sport in the V6 turbo hybrid era and are prepared to take the penalty in a race they don't expect to compete.
Button told Sky Sports: "It's really tricky because you'd normally run a lot of downforce here, because there's a lot of low-speed corners.
"For the engines, it's tough as well, with the compressor - and for us it's going to be very difficult this weekend.
"Because of our compressor, it will be the toughest race for us possibly."
McLaren are languishing ninth in the Constructors' standings, while their drivers Button and Alonso are 16th and 17th respectively in the Drivers' Championship.
And due to the high altitude of the Autodromo Hermanos Rodriguez circuit, their cars are expected to face further issues this weekend, as reliability becomes an issue with the cars' turbochargers expected to spin faster due to thinner air.
The 35-year-old added: "It's not a great way to start the weekend but it's going to be a very difficult weekend for us anyway, because of the altitude.
"We don't expect to be competitive here. I don't expect us to be fighting for points."
It is expected to go from good to bad for Button, with the Brit having made his best finish to a race this season at the US Grand Prix last weekend - in sixth - after Toro Rosso's Carlos Sainz time penalty demoted his position on the leaderboard.
Despite not expecting to compete much in this weekend's race, McLaren will be hopeful they can finish the season above Sauber, who are currently nine points above them in eighth.