Ferrari's Alonso fastest in final practice at Singapore GP, ahead of Ricciardo, Rosberg

Ferrari driver Fernando Alonso of Spain, left, walks with Lotus driver Romain Grosjean of France, right, after the second practice session for the Singapore Formula One Grand Prix on the Marina Bay City Circuit in Singapore, Saturday, Sept. 20, 2014. (AP Photo/Aaron Favila) (The Associated Press)

Mercedes driver Nico Rosberg of Germany arrives for the third practice session of the Singapore Formula One Grand Prix on the Marina Bay City Circuit in Singapore, Saturday, Sept. 20, 2014. (AP Photo/Aaron Favila) (The Associated Press)

SINGAPORE – Ferrari driver Fernando Alonso set the fastest time in Saturday's final practice session for the Singapore Grand Prix, with Red Bull's Daniel Ricciardo second.

The pace of the Ferraris and Red Bulls suggested they could challenge the Mercedes drivers — who have taken all but one pole position this season — in qualifying at Marina Bay later in the evening.

Mercedes' Nico Rosberg was third fastest and his teammate and championship rival Lewis Hamilton was sixth, separated by Toro Rosso's Jean-Eric Vergne and Red Bull's Sebastian Vettel, who has won the past three races in Singapore.

There was improvement from the Williams drivers, who were well off the pace on Friday. Felipe Massa was seventh, ahead of teammate Valtteri Bottas.