Michael Schumacher [Images], enduring one of the longest winless streaks of his Formula One career, is not having fun in the sport he long dominated and may retire soon, his brother Ralf said on Wednesday.

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"I don't believe that Michael will be driving for very much longer," Ralf said in an interview with Sport Bild newspaper of the seven-times world champion, including the last five titles for Ferrari [Images].

"He'll stay as long as he's having fun with it. The success in past years was obviously a lot of fun for him. He's not having that fun at the moment and I'm very anxious to see what will happen if it stays like that until the end of the season."

Schumacher, 36, has a contract running through the 2006 season and has said he will keep racing for as long as he is still enjoying himself.

Schumacher has struggled badly this year, however, awaiting his 84th grand prix victory for more than eight months.

It is the longest winless spell for the German since 1993, excluding 1999 when he was sidelined with a broken leg.

Schumacher won 13 of the 18 races last season but has not finished higher than second in 2005. Schumacher is in fifth place in this year's championship, 35 points behind Renault's overall leader Fernando Alonso [Images] with 11 races remaining.

"Ferrari have passed their zenith," said Ralf, adding that Ferrari's problems were not just to with their tyres. "They've did a great job in past years but they're not doing it anymore.

"Mistakes have crept in other areas (aside from tyres). It can be seen as a sign of weakness that Ferrari introduced their new car so late in the season. I'm not sure whether someone who has had such a successful time, as Ferrari has had, can still have the bite to fight back to the top."

Ralf, who drives for Toyota and lives in Austria, said he also expects a lot of top people around his brother to leave Ferrari once he retires.

"When Michael leaves then a lot of good people will leave at the same time," Ralf said. "After that it will be very difficult for Ferrari to get back to the top. I'm not sure that would even be possible."

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