Ross Brawn has painted a clear picture as to what made Michael Schumacher a seven-times champion in contrast to Jenson Button.

All that was required was Schumacher's 90 minutes of track time on Monday as he made his long-awaited comeback after more than three years in retirement.

For Mercedes GP boss Brawn, the technical guru behind all of 41-year-old Schumacher's championships, he admitted it was a return to the good old days.

Schumacher claimed he felt like a kid with a new toy following his first serious outing in a Formula One car since the Brazilian Grand Prix of 2006.

Brawn described the first day of testing of the Mercedes as "OK," which was hardly a ringing endorsement of the new 'Silver Arrow'.

However, working with Schumacher again at least brought memories flooding back, and a realisation if improvements need to be made, the German is the man to help make them.

"He was very enthusiastic, and it was good to see that enthusiasm," said Brawn of Schumacher, who finished third quickest at the end of the day behind former Ferrari team-mate Felipe Massa.

"It would have been more of a surprise if he hadn't been where he was, so it was confirmation of what we both thought - that he should be competitive."

Reflecting on Schumacher's strengths compared to those of Button and his Brawn GP team-mate of last season in Rubens Barrichello, Brawn's response was unequivocal.

"What came through was Michael's precision about what's going on in the car, what he wants and what he feels is needed," added Brawn.

"He has great clarity of reasoning in what he does, what he feels and what he thinks should be the direction we take or changes to come.

"That's always been notable about Michael in his career, and that's probably the most noticeable difference.

"Both Rubens and Jenson gave very good information on the car, and that was never a problem.

"It's just that Michael is more precise in his opinions as to what is happening.

"That's nice to work with again. It was a bit like the old days."

With team-mate Nico Rosberg in the car for Tuesday's second day at the Ricardo Tormo circuit in Valencia, Schumacher will enjoy a full day of running on Wednesday.

That is likely when he will begin his methodical analysis of a car he will naturally hope can carry him to an eighth title.

For now, following his 40 laps yesterday, Schumacher left the track in a positive mood.

"At the moment he is fairly happy with the car, and has not really pinpointed any areas we need to work on," added Brawn.

"But I'm sure as he gets into it more and starts to find the limits of the car more, then he may have stronger opinions on the areas we need to improve.

"We're all optimistic, and I'm sure he is, that there is still a lot more to come.

"He hasn't driven a Formula One car seriously for three years, so it was pretty encouraging."