Schumacher holds off Webber's Red Bull in Bahrain
Mercedes boss Ross Brawn has admitted that his team are not on the pace and that it will be some time before they can compete at the front.
Nico Rosberg and Michael Schumacher were fifth and sixth in the season-opening Bahrain race, 40 seconds behind winner Fernando Alonso's Ferrari.
"We accept we were not competitive enough and we have work to do to close the gap to the leaders," Brawn said.
"We have a development plan that should bring the required improvements."
Brawn insisted that the Mercedes car was "fundamentally strong" and added that he was "pleased" with the performance of both drivers.
I'm looking forward to Melbourne - I think we'll go well there
Rosberg was the faster of the two Mercedes drivers in Bahrain, qualifying in fifth place 1.140 seconds behind the pole-sitting Red Bull of Sebastian Vettel.
Schumacher, in his first race back after three years in retirement, was 1.423secs behind Vettel in seventh place on the grid, but was more competitive in the race, matching Rosberg's pace in the final stint.
Ferrari, Schumacher's former team, started the season in style, with Alonso leading team-mate Felipe Massa over the line for a one-two after Vettel's leading Red Bull hit problems.
Schumacher said he was "very happy" with the outcome of the Bahrain race.
"Sixth position was good for me, especially considering how many times I have driven an F1 car since my retirement," he said.
Mercedes won last year's world titles in their previous guise as Brawn.
The team have been further hit by a report that they will have to alter their car's design for the next race in Australia on 28 March.
Autosport has reported that governing body the FIA has asked Mercedes and McLaren to alter their diffusers - a crucial aerodynamic part at the rear of the car - because their design was against the spirit of the rules.
McLaren, meanwhile, are hopeful of a more competitive showing in Australian than they managed in Bahrain.
Their drivers, Lewis Hamilton and Jenson Button, were also more than a second off the pace in qualifying, although Hamilton was able to match the times of the Ferraris once he was in clear air in the race.
Hamilton said: "I'm looking forward to Melbourne. I like the circuit, I think we'll go well there and I don't think we'll have the same problems that slowed our progress in Bahrain."