Mercedes revealed on Friday that Lewis Hamilton is likely to be in for a tough season as the seven-times world champion has already lost one of his four allotted engines, meaning he could face grid penalties later in the season.
Hamilton is in his final season with the Silver Arrows before he joins Ferrari next year. He retired from the Australian Grand Prix after a sudden power unit failure.
"That one is for the bin," Mercedes' boss Toto Wolff said during the opening sessions for the Japanese Grand Prix at Suzuka circuit.
"It is a very highly unusual failure that we have a hardware failure that we didn't see coming before. So yeah, we can't reuse that. And it depends how the season develops, whether we need one more or not. I can't really say at this stage."
Meanwhile, Wolff made a U-turn on his decision not to attend the Japanese GP.
The Mercedes team boss was scheduled not to be at Suzuka this weekend. The Press Association reported it was planned before the start of the new season and not as a result of the team's poor performance at the Australian GP.
Neither Hamilton nor George Russell finished the race in Melbourne, with Russell's fifth-placed finish in the season-opener in Bahrain their best result this year.
Mercedes have struggled since new regulations arrived in 2022. Wolff changed his mind on attending the race in Suzuka where Russell and Hamilton finished fourth and fifth in first practice before a rain-affected second session.
"I had planned not to come to Japan, because there's so much on back in Europe, things to do," he said.
"But then I felt not coming to Japan was the wrong choice. I think it's important to be with the race team...it does me good also, to be close to the action.
"We're experimenting with a few things and then being part of the team really gives me energy and I hope the other way around, too. So that's why I decided against staying in Europe."
At the track, Max Verstappen went fastest on Friday in the first practice.
Triple world champion Verstappen, who failed to finish the race in Australia a fortnight ago, edged Red Bull team-mate Sergio Perez in dry conditions in the first session in Suzuka.
But it was a different story later in the day when only five drivers recorded a timed lap in on-off showers, with McLaren's Oscar Piastri going quickest ahead of Hamilton.
Verstappen and Perez did not come out for the second practice.
They were among several drivers who remained in the garage as the teams tried to preserve their tyres in the tricky conditions.
"In FP2 we couldn't do anything, which was a shame as this means that we don't know the long-run pace, but we can't do anything about the weather," said Verstappen.
"In general, it looks like everyone is a bit closer compared to last year and I don't expect the same kind of gaps here at this track."
Verstappen won the first two grands prix of the season but the Dutchman retired from a race for the first time in two years in Melbourne after a brake issue.
Normal service resumed in the first practice, in a session that was red-flagged for around 10 minutes after Williams driver Logan Sargeant crashed into a wall of tyres.
