Alonso and Button vent after Suzuka struggles

Struggling with a lack of engine performance, Alonso and Button finished their engine supplier's home grand prix in 11^th and 16^th respectively, both being passed with ease by rival cars throughout the race.

"They pass me on the straight like a GP2," said an exasperated Alonso on team radio during the race. "Embarrassing, very embarrassing." 

Later, he reiterated: "GP2 engine. GP2… arrrgh! All the drivers we are racing with, unbelievable."

Speaking after the race, Alonso described his annoyance in more detail: "It's frustrating how they overtake you on the straights and then you arrive at the corner and you see them braking late, making mistakes.

"You take the corner perfectly and you are recovering time but they just overtake you on the straights."

But, when asked if he would definitely remain at McLaren in 2016 if things had not improved by the end of the year, Alonso said: "The remaining races will be tough, but it's progress next year we're looking for and my intention is to stay for sure and to win.

"I am sure we will win together but the matter is when, and we need to make this tough time as short as possible."

Button: "I was a sitting duck"

Button, meanwhile, said he was powerless to stop his rivals flooding past, and suggested that the difference in speed between the McLarens and the others along the main straight was a safety issue.

"The problem was I made the mistake of pitting after [Marcus] Ericsson, he was behind me and he got in front," he explained. "He wasn't fast and I couldn't overtake him.

"The pace was good and I was catching Fernando in the last stint, got I stuck behind Ericsson and then I didn't have the buffer of Ericsson when everyone came out of the pits and were super-fast.

"I was just a sitting duck, was getting overtaken into 130R. I needed a NOS button to keep people behind!

He added: "There's such a difference in speed, they go for moves in 130R and I think 'it's not going to happen', but they can see the speed difference whereas in the mirrors I can't.

"The problem is the closing speed was so great, it could have been a massive accident.

"They've got DRS, they're 30, 40 km/h quicker, and trying to judge that is very difficult for all of us."

Asked if he intends to stay at McLaren next season amid intense speculation about his future, Button: "We've got a lot of work to do. It's so tough because [Fernando and I] are used to fighting, but we're not even fighting.

"It's like a samurai without his armour and sword."