"We are not in the position we would like to be," the 41-year-old Schumacher told reporters.
"The main issue for now is not to be too far off," added the German, who is returning to the sport after three years in retirement.
Schumacher was seventh quickest with just two days of official testing remaining in Barcelona [ Images ] before the season-opening race in Bahrain on March 14.
Mercedes bought last year's world champions Brawn before recruiting the German but the new Ferrari and Red Bull cars have impressed the paddock the most.
However, times in testing are misleading because teams are practising with different fuel loads given refuelling will be banned in races this season.
"There are no reasons to not talk about us being able to be competitive in the championship," he said.
"It is a very good atmosphere (in the team). Age does not matter. I don't feel what it says on my passport," he added.