Schumacher was in action at the Spanish circuit on Friday and Saturday, finishing first and third. However, on both days his best times were one-offs as the German struggled to find a consistent pace with his new W02.
In fact, on Friday when he finished at the front of the pack, Schumacher's average lap time put him outside the top half of the field.
"Yes, we are slightly concerned but then on the other hand we know where we will and want to go to," the 42-year-old told the BBC.
"The first race will tell us truly what is the situation."
Mercedes have already made it clear that their target is to win the F1 World titles, however, Schumacher reckons that's going to be a difficult task this season, especially at the start.
"For the team it is very important to climb the ladder and have more success than last year.
"We are Mercedes and we have a very clear target. It is going to be difficult to meet this target straight away this year particularly after last year's experience.
"But it is a programme and a vision for more than just the short term."
One aspect that will have an impact on Mercedes GP's season are the new Pirelli tyres, which Schumacher says Merc still need to get a handle on.
"We have a character of car that we built up," he said, "but we have a new character of tyres and how much they will be in harmony is difficult to say at this moment in time.
"It seemed less important last year and is more important this year."
Source: http://www.planetf1.com