Heikki Kovalainen will spend another week recovering from a head injury sustained recently.

The Lotus driver was ordered to bed early last week after medical checks showed he suffered a heavy concussion when he crashed an Audi R8 during the Race of Champions event in Dusseldorf.

Kovalainen, who was knocked out in the crash while his girlfriend suffered minor injuries, wrote on Twitter that his recovery is “going well”.

“Final scans for the head done today, no problems and just one more week resting then back to fitness training!” reported the 29-year-old Finn.

Nick Heidfeld shouldn’t feel down after being comprehensively outpaced by his teammate on his return to formula one, according to team boss Peter Sauber.

The German, who has been test driver with Mercedes and then Pirelli for most of 2010, was disappointed in Singapore on Saturday to significantly trail the pace of the Swiss team’s regular rookie Kamui Kobayashi.

Heidfeld, 33, was particularly unhappy with Saturday night’s result, having looked a match for Kobayashi under the artificial lights until the decisive knockout session.

But Sauber told Auto Motor und Sport: “We expected too much of him, and he expected too much from himself.

“He has been out for a year and didn’t know the car or the tyres, and Singapore is an extremely difficult track.  That explains the gap to Kamui, even if it is a second,” added Sauber’s founder and boss.

Heidfeld has also joined the ranks of drivers who do not instinctively enjoy Bridgestone’s 2011 generation of tyres.

“My first impression is that I got along better with last year’s tyres,” he said.

Sauber is quoted in Singapore by Germany’s Speed Week: “This weekend is for him to settle in so I will not judge him yet.”