BERLIN, Germany - World champion Sebastian Vettel said on Thursday, October 4, 2012 he was saddened to hear that compatriot Michael Schumacher has decided to again retire from Formula 1.The 25-year-old Red Bull driver, after hearing Schumacher will retire at the end of the season when his Mercedes deal expires, said: "This is a shame and a great loss for F1. In the last three years we had a lot of fun with him. 'SOMETIMES TOUGH, ALWAYS FAIR'"For a long time, his return might not have gone the way he imagined it would. But I think the car simply didn't produce enough and he couldn't strut his stuff like he used to."According to Vettel, Schumacher no longer had to "prove anything to anyone" after the 43-year-old decided to quit for a second time having first retired in 2006, then returned in 2010 after signing a three-year deal with Mercedes."For me he is still one of the greatest. It was always special to race against him," said Vettel. "On the track, he was sometimes tough, but always fair."Vettel said he now hoped to see his idol next season "in a different capacity, but still on the track".Schumacher's Mercedes team mate Nico Rosberg also said he regretted Schumacher's retirement.Rosberg said: "This is a huge loss for our sport, many fans have been following his return to F1 with interest. "I am very, very lucky that I had him as a team mate for three years. I have huge respect for his achievements."He was out of F1 for three years; that is so hard to comeback again and reach the level he is at now."Having won the last of his seven world titles in 2004, Schumacher's best finish this season was third at Valencia's European Grand Prix in June.