It’s been a tumultuous Formula 1 season for former world champions Fernando Alonso and Jenson Button, who have scored just 17 championship points combined through the first 14 races of the year. Engine supplier Honda returned to the sport in a partnership with McLaren in 2015, but despite the talents of both Alonso and Button, the team’s cars simply haven’t been quick enough to compete with the rest of the field, and Alonso’s frustration bubbled over during Sunday’s Japanese Grand Prix at the Suzuka Circuit.

Shizuo Kambayashi/AP

Alonso qualified 14th and jumped up the field at the start, running inside the top 10 — but it was all downhill from there. Both Alonso and Button were severely overmatched on the long front straight at Suzuka, and after being continually passed Alonso compared the Honda engine’s power to one used by GP2 cars, a Formula 1 feeder series.

“I’m getting passed down the straight like a GP2, this is embarrassing. Very embarrassing.”

This isn’t the first time this season Alonso has aired his grievances over the team radio during a race, but his open criticism of the car especially controversial given that Suzuka is Honda’s home track. Alonso would go on to finish 11th, while Button settled for 16th.

Hours later, Alonso addressed his radio communications from the race and reiterated that he plans to stay with McLaren-Honda.

Button was rumored to be mulling retirement after the season, but McLaren Group CEO Ron Dennis said Sunday that he expects both Alonso and Button to return for 2016, as both are still under contract. If the team can’t provide competitive equipment, however, it’s hard to imagine that Alonso will be satisfied running in the back of the pack for another two seasons.