George Russell's long-shot title bid took another hit before Formula 1 even reaches Singapore. The Mercedes driver is set to take a new power unit this weekend, which puts him over the season limit of four and triggers a grid penalty for Sunday's race, Sky Sports and Motorsport.com reported.

Russell's engine failed late in the Bahrain Grand Prix, held this year at Sepang in Malaysia, while he was running third with five laps left. Teammate Kimi Antonelli finished second, and Max Verstappen won for the first time this year, F1.com said.

"It's clearly a mechanical failure on the power unit side," Mercedes deputy team principal Bradley Lord said. Mercedes had hoped to take the penalty later, likely in Austin, when it plans to fit an upgraded engine, Motorsport.com said.

The penalty applies only to Sunday's Grand Prix, not Saturday's Sprint. That matters, because Marina Bay is one of the hardest tracks on the calendar for passing. Antonelli overcame a similar penalty at Monza in September, winning his home race from 19th on the grid.

The title math still favors Antonelli. He has 320 points to Russell's 236, with Lewis Hamilton third at 214, GPBlog reported. There are 183 points left. Even if Antonelli wins the Sprint and the race while Russell scores nothing, the gap would be 117 with 150 points still to play for. That means the United States Grand Prix in Austin on Oct. 25 is his first chance to clinch.

Singapore holds the last Sprint of the season. The Sprint starts at 5 p.m. local time Saturday, which is 5 a.m. ET, and the Grand Prix starts at 8 p.m. local time Sunday, or 8 a.m. ET, according to F1.com. The forecast calls for heat, humidity and a chance of rain on Friday and Saturday, but a dry Sunday.

What we know: Antonelli leads by 84 points and cannot win the title this weekend.
What we don't: Exactly where Russell will start on Sunday.