London: Nick Heidfeld looked ever more likely to replace Robert Kubica at Renault after setting the pace in Formula One testing at the Jerez circuit in southern Spain on Saturday.
The German, already the frontrunner to stand in after the Pole suffered career-threatening injuries in a rally crash in Italy last weekend, seized his chance with both hands on his first day back in a Formula One car since November.
The 33-year-old, who was Kubica`s team mate at BMW-Sauber for the best part of four years, ended the day with the fastest time and a best lap of one minute 20.361 seconds in the new R31 car.
Renault have said Heidfeld, vastly experienced with a decade in the sport and 172 starts, is on pole position to replace Kubica for part or all of the season.
"If we are happy with Nick then we keep Nick," team principal Eric Boullier said on Thursday. "We have to develop this car from scratch so the obvious choice of driver is an experienced one."
The German said he enjoyed his experience on Saturday.
"It was fun driving the car although it obviously takes time to get used to things when it`s your first time in a car and working with a new team," he said.
"We had a good day, without too many problems, and luckily all the changes we made to the car went in the right direction and improved things so I was able to push harder and harder."
Ferrari`s Spaniard Fernando Alonso, whose presence caused traffic jams in the morning as thousands thronged to the circuit, was second fastest.
Alonso, Kubica`s good friend and regular paddock poker partner, lapped with an image of the Pole`s helmet on his own and did 131 laps.
Kubica had more surgery on Friday after a seven-hour session on Sunday and is sure to be out for at least the first three months of the season which starts in Bahrain on March 13.
Doctors said the 26-year-old is likely to need one further operation.