By Steve Keating
AUSTIN, Texas (Reuters) - Heikki Kovalainen has been around Formula One long enough not to get excited about Friday practice times but Lotus were singing his praises after their Finnish stand-in's impressive performance at the U.S. Grand Prix.
The veteran of 109 Formula One races, the last 60 without scoring a point, Kovalainen was fifth fastest at the end of the opening day and ahead of French team mate Romain Grosjean on the timesheets.
"We feel he's done a brilliant job today, particularly with all the procedures and getting used to driving a new car," declared technical director Nick Chester.
"We felt it might take a little bit of time. But actually straight away in P1 (first practice) he was already looking after the car very well and in P2 he was fifth quickest and good long runs, I think he's done a great job today."
Kovalainen has not raced since he left Caterham at the end of last year, although he has taken part in some Friday sessions for that struggling team.
With compatriot Kimi Raikkonen undergoing back surgery and ruling himself out of the last two races, Kovalainen got a call from Lotus principal Eric Boullier on Tuesday asking if he was interested in stepping in.
So late was the summons that he had to miss a scheduled news conference on Thursday at the Circuit of the Americas, and he was also delayed on Friday by fog that forced practice to be truncated.
A former driver for Renault, Lotus's predecessors, Kovalainen looked very much at home and ended the afternoon just 0.768 seconds behind Red Bull's quadruple world champion Sebastian Vettel.
It was the type of performance that had the paddock buzzing on a sunny Texas afternoon with talk of top four spot on Sunday's starting grid.
"It's better not to speculate too much," Kovalainen cautioned. "It could be a disaster or could be good. You never know, I don't like to speculate.
"I think the main thing is that if we can improve from today a little bit, chip away slowly and get the best out of the car. If we fall off a little bit it is so close you could easily be out of the top 10."
A race winner with McLaren in 2009, Kovalainen's experience is just what Lotus need as they battle Ferrari and Mercedes for second place behind Red Bull.
"They hired me to score some points, I felt personally that I should be able to do the job," said Kovalainen. "It's nice to be chasing the Ferraris and the McLarens and even the Red Bulls in the longer runs, going past some of the cars.
"But you never know about a short transition from one team to another. You never know how things will work out," he cautioned.
"Today they worked out quite well but tomorrow could be a disaster. We can't take anything for granted."
(Editing by Alan Baldwin)