Mercedes boss Toto Wolff thinks the recent spate of engine failures suffered by Ferrari shows how hard it is pushing to beat his team.
After engine failures on both cars in Malaysia prompted an organisational change within the team's engine department, Sebastian Vettel's hopes of cutting Lewis Hamilton's title lead evaporated in the early stages of the Japanese Grand Prix. Ferrari detected a spark plug issue on the grid but did not have enough time to rectify the problem, meaning Vettel quickly fell back from second once the race started. Vettel retired on the fourth lap and Hamilton won, opening up a 59-point lead four races to go.
The failures have coincided with Ferrari showing a step in performance with its car, which was comfortably quickest in Singapore and Malaysia. Wolff sympathises with Ferrari's situation but says finding performance can always come at the expense of reliability.
"In this sport you take no prisoners," Wolff said. "It is about having the fastest car, the best driver and the most performance. We have been there. We have had difficult moments for each of the drivers in the past in terms of reliability.
"When you are pushing the boundaries you will eventually reach the limits. Ferrari's development from 2016 to 2017 was exceptional and probably this is a development phase. I can, nevertheless, relate to how it feels having had three races where you've lost a lot of points. It doesn't feel nice."
Mercedes has put a lot of focus into improving reliabilty after a spate of engine failures across last season cost Lewis Hamilton the 2016 crown, though on that occasion his only rival was teammate and eventual champion Nico Rosberg, meaning the team still claimed the title.
Wolff said those failures helped the team achieve the good reliability level it has enjoyed this season.
"There is a saying that in order to finish first, [first] you have to finish. But nevertheless it is part of the learning curve of any team. You are chasing performance and you are trying to make it reliable. They have certainly found the performance and now they are making it reliable, but I don't know a lot of what's happening [at Ferrari].
"I'm happy that we have kept it together and our quality people and designers have done an exceptional job in making us very reliable this year. But there are four more races to go, so let's clap on our back once those races are done."