Formula One leader Lewis Hamilton had the fastest time in Friday’s practice for the inaugural Russian Grand Prix as the Red Bulls of Daniel Ricciardo and Sebastian Vettel struggled.

Hamilton was second in the morning session behind Mercedes teammate Nico Rosberg but dominated the afternoon run by a wide margin. Rosberg dropped to fourth.

Kevin Magnussen of McLaren was second, with Ferrari driver Fernando Alonso third. Valtteri Bottas of Williams was fifth behind Rosberg, with Jenson Button in the second McLaren completing the top six.

The second session was red-flagged for several minutes towards the end after Ricciardo stopped on the track with a power unit failure. His departing Red Bull teammate also reported issues and the defending world champion placed ninth.

Hamilton’s fastest lap of 1 minute, 39.630 seconds on the Sochi Autodrom, built around the Olympic Park that was used for the Winter Games in February, was an improvement of nearly three seconds from his morning run on the unfamiliar circuit making its debut on the Formula One calendar.

Mercedes can clinch the constructors’ title with a victory in Sunday’s race. Hamilton leads Rosberg by ten points in the drivers’ standings.

The Marussia team ran only one car out of respect for driver Jules Bianchi, who remains in critical but stable condition with severe head injuries after crashing into a mobile crane at the Japanese GP last Sunday.

Bianchi’s father, Philippe, told the newspaper Nice Matin that “Jules is fighting as he always did, the same way as if he was racing. He is strong.”

With the French driver’s car in pit lane, Marussia’s other driver, Max Chilton, placed last in the first practice.

“It is going to be a very emotional weekend for the whole team, but we will try to get through it and keep praying for Jules,” Chilton said.

Alonso’s car bore a sign saying “Forza Jules” (Go Jules), while other drivers had a sticker on their helmets saying in French “Tous avec Jules” (Everybody with Jules).