Alonso qualified inside the top 10 at Suzuka, but will drop to the back of the grid thanks to a 35-place penalty incurred ahead of final practice on Saturday.

Honda discovered a hydraulic leak on Alonso's engine after Friday practice and elected to swap the power unit in its entirety rather than attempt a fix.

Teammate Stoffel Vandoorne will start ninth, and a grid penalty for Ferrari's Kimi Raikkonen means both McLaren-Hondas could have started the Japanese Grand Prix in points contention but for Alonso's setback.

"I'm very ashamed," Hasegawa told reporters after the session. "We didn't have an engine failure, we had some hydraulic leakage, which we can change if we find out [the cause] with enough time, but we couldn't, that's why we need to change the engine."

McLaren-Honda had to break curfew regulations for the second time this season to complete the engine change, which racing director Eric Boullier said was "frustrating for everybody" and "does affect the preparation for the weekend in terms of pitstops and practices, so it's not ideal".

Alonso now faces an uphill battle to recover a decent result in the last Japanese GP before the current McLaren-Honda alliance is dissolved at the end of the season.

"With all the high-speed corners it will be difficult to follow the [other] cars and will be a tough race," Alonso said. "Hopefully we can do a good start and play a good strategy and we'll see how the pace is.

"We need some speed to overtake cars on the straights, which normally we don't have, so it's going to be [a] demanding, complex race to execute.

"There are not really any clear targets. Hopefully close to the points will be good."