Kovalainen told the Finnish newspaper Turun Sanomat he also cannot be sure that McLaren's gamble on Magnussen will pay off.
"I don't understand how I could make so many mistakes," said Kovalainen.
Heikki Kovalainen: "I think the car is great, but I was not able to unlock the pace."
Romain Grosjean's RS27-2013 engine failing in spectacular fashion on what would be the final appearance for the V8 configuration power plant.
Romain Grosjean putting in a respectable lap in the final moments to take sixth on tomorrow’s grid. Heikki Kovalainen narrowly missed the cut for the top ten shootout in eleventh.
Romain Grosjean was tenth fastest on a day which started wet and became wetter with rainfall over the Brazilian track in São Paulo.
Mercedes’ Nico Rosberg on top again at Interlagos as he delivers repeat performance.
Heikki talks about Austin and Interlagos.
A difficult afternoon for Heikki Kovalainen saw the Finn drop to fifteenth from his eighth place grid slot.
The E21 demonstrated strong potential using both tyre compounds. Heikki was quickly up to speed.
According to sources inside the Lotus team, Finn Kovalainen will shortly be announced by Lotus as Raikkonen's replacement for the last two Grands Prix of 2013.