Rubens Barrichello has revealed he has been impressed with the step forward taken by Team Lotus for 2011.
Lotus finished its debut season as the best of the three newcomers, but still significantly off the pace of the established teams.
"Lotus were four seconds behind Red Bull in 2010," Williams driver and Grand Prix veteran Barrichello told O Estado de S.Paulo newspaper.
Lotus were four seconds behind Red Bull in 2010
"They seem to have improved two seconds for this year."
Little can be said about HRT's untested new F111 car, but Barrichello has admitted he is worried for the Virgin team.
"With the return of the 107 per cent rule, it is possible that a few times they will not qualify. At the moment they seem slow," said the 38-year-old.