Lewis Hamilton fears more reliability problems could thwart his attempt to catch Mercedes team-mate Nico Rosberg in the drivers' championship.
Hamilton is 43 points behind Rosberg after finishing second to him in Sunday's Russian Grand Prix.
The Briton said: "My concern is not about beating Nico. My concern is more the guys giving me a car to be able to fight equally.
"Do I think it is not going to happen again? No. There'll be problems ahead."
Hamilton's remarks are a reference to the series of reliability problems that have hit him in the last two races.
In Russia, an engine failure in qualifying left him 10th on the grid. He fought back to second after Mercedes flew in fresh parts and his mechanics worked through the night to fit them.
Hamilton had another engine problem during the race in Russia. He had closed to seven seconds behind Rosberg and was entertaining thoughts of winning the race when the team told him to back off because his engine was losing water pressure.
The Briton said: "I'm not sure I've ever been big believer in luck. There is a reason for everything. What those are, I don't know.
"I am not hoping for it to get better, I am just going to keep doing what I'm doing. I am doing the job as well as I can do."
Hamilton would need a victory and a second place - without Rosberg scoring a point - to draw level with the German.
Hamilton said: "He has a buffer knowing even if he has two bad weekends he is still in the fight, which is a huge confidence boost.
"Generally he has been starting at the front with no-one to really both him so it has been a nice Sunday drive for him.
"But there are still 17 races to go, and still 17 races I can give him hell."
Rosberg said: "For sure it is a lot of points but there is a long way to go. Lewis is as strong as ever and it will be the usual tough battle with him. It is just about going race by race at the moment."
Mercedes F1 boss Toto Wolff has described the failure that hit Hamilton on Saturday in Sochi as "freak" and has pledged that the team will work out what is going wrong.