Schumacher rumor mill in overdrive

The European racing press is agog with speculation that seven-time Formula One world champion Michael Schumacher is poised to make a comeback, potentially driving for his old team boss Ross Brawn and the newly rebranded Mercedes F1 team. And there is certainly plenty of circumstantial evidence to support the notion that Schumi could return to the sport he dominated for more than a decade.

Schumacher, 40, has casually raced motorcycles since stepping away from the Brawn-managed Ferrari F1 team at the end of 2006. The German was ready to step back into a Ferrari a few months ago when Felipe Massa suffered a season-ending skull fracture, only to have his comeback effort halted by complications from a neck injury he suffered in a 2008 motorcycle racing accident.

Since his retirement from the cockpit, Schumacher has served as an ambassador for Ferrari, and he recently extended his contract with the Italian automaker for an additional three years. But that hasn't slowed down the Mercedes rumors, and the German publication Bild reported last week that Schumacher was set to meet with his manager, Willi Weber, in Stuttgart, Germany -- the home of Daimler-Benz headquarters -- on Monday.

In addition, Schumacher says he has completely recovered from the neck injury and has recently competed in a series of high-profile kart races, including the SKUSA SuperNationals in Las Vegas and Massa's annual charity event in Brazil.

There is no question that despite his advanced age in F1 terms, Schumacher would be competitive should he decide to return to the sport. And there are certainly precedents: Over the past 30 years, half a dozen former F1 champions returned to the Grand Prix grid, including a pair who went on to win additional world titles. And 1972 and '74 world champion Emerson Fittipaldi went on to have a successful post-F1 career in Indy car racing -- the Brazilian won the 1989 CART championship and two Indianapolis 500s in his "second" go-round.

Here's how six former F1 champs fared on their return to the top level of the sport, ranked by level of success:

Niki Lauda: Best known for surviving a fiery accident during the 1976 German Grand Prix at the Nurburgring, 1975 and '77 world champion Lauda literally walked away from F1 during practice for the 1979 Canadian GP, claiming he was "bored of driving around in circles." After focusing on his startup airline for a couple of years -- and perhaps motivated by the need for cash to fund it -- Lauda returned to F1 with the McLaren team in 1982. He won his third race back and finished fourth in the championship, then endured a comparatively poor 1983 season when McLaren did not enjoy the benefit of a turbocharged engine.

Armed with turbo TAG-Porsche power in 1984, Lauda added a third championship to his legend, edging his new young-gun teammate Alain Prost by half a point. Prost then dominated the 1985 season, winning six races to Lauda's one, prompting the Austrian great to retire again, this time for good.

Alain Prost: The diminutive Frenchman was F1's dominant driver in the 1980s, winning the 1985, '86 and '89 championships for McLaren. When McLaren began to obviously favor rising star Ayrton Senna, Prost moved to Ferrari and came close to winning the 1990 title. But the 1991 Ferrari was a bad car, and Prost was dropped by the team after comparing its handling to a truck. Williams wanted to sign him up, but incumbent driver Nigel Mansell vetoed the move, and Mansell went on the win the 1992 F1 crown for Williams-Renault while Prost took a one-year sabbatical from F1.

However, Mansell was unable to come to terms with Williams for a contract extension -- mainly due to his refusal to race alongside Prost, who had been his Ferrari teammate in 1990. Williams cut ties with Mansell, opening the door for Prost to return to secure a fourth F1 championship in 1993. But once again, Senna proved to be a thorn in Prost's side, and when Williams signed Senna for the '94 season, Prost decided to quit F1 for good. He contemplated another F1 comeback, testing for McLaren in 1996, but ultimately stayed away, competing instead in ice racing.

Nigel Mansell: After his hardball tactics left him without an F1 ride for 1993, Mansell competed in the CART IndyCar World Series for Newman/Haas Racing. Remarkably, Mansell won four oval races and the CART championship, but he soured on IndyCar racing in 1994 when Newman/Haas' new Lolas were uncompetitive against the three-car Penske Racing attack.

When Senna was killed early in the 1994 season, Mansell saw his opportunity to return to F1 with Williams. He made a one-off start midseason in the French GP, then came back for the final three races of '94, taking a lucky win in the Australian GP. Once again dropped by Williams, Mansell signed to drive for McLaren in 1995, but it was a mismatch from the start. He missed the first two races of the '95 campaign when he did not fit in the McLaren. A wider chassis was designed and built, but Mansell made just two starts for McLaren, ending his F1 career in ignominious fashion.

Mario Andretti: Mario won the 1978 world title for Team Lotus, but in typical Lotus peak-and-valley fashion, the next two years were disastrous for Colin Chapman's team. Andretti moved to Alfa Romeo for the 1981 F1 campaign, but he failed to find success, and in 1982, he returned to America to compete in Indy cars full time for the first time since 1974.

But Andretti's F1 career wasn't quite done. When Carlos Reutemann suddenly retired in early 1982, Mario was drafted in by the Williams team, and he made a one-off start in the Long Beach Grand Prix. Later in the year, the injury-ravaged Ferrari team came calling, drafting Andretti in for the final two races of the '82 season. Back with the team that he competed in F1 for in the early '70s, Mario made a triumphant return, claiming pole position and finishing third in the Italian GP. He remained a front-runner in Indy cars until he retired at the end of the 1994 season.

Jacques Villeneuve: 1995 CART champion Villeneuve joined Williams, the top F1 team of the time, in 1996 and won the world championship in his second attempt. A switch to the BAR (later Honda) team for 1999 proved disastrous. Villeneuve never came close to winning another F1 race, and he was dropped by Honda prior to the end of the 2003 season.

Villeneuve was tapped by the Renault team to replace Jarno Trulli for the last three races of 2004, but his performances (a pair of 10th places) paled in comparison to future world champion Fernando Alonso. Still, he was retained by the Sauber team in 2005, but midway through 2006, with the team now operated by BMW, he was replaced by Robert Kubica. Villeneuve still pines to compete in F1 and is attempting to secure a slot on the 2010 grid with one of the new teams entering the sport.

Alan Jones: This burly Australian helped build Williams into a top F1 team and won the 1980 world championship, but an unhappy relationship with teammate Carlos Reutemann prompted him to quit the sport at the end of 1981. Overweight and out of shape, Jones made a one-off return for the Arrows team in the 1983 Long Beach Grand Prix.

Then Carl Haas, for whom Jones competed in the SCCA Can-Am series in the late '70s, hired AJ to drive for his startup Beatrice/FORCE team. Jones made three starts for Haas' new team in late 1985 and competed full-time in the 1986 championship, but the Ford-powered car was uncompetitive and Jones scored only four points. He returned to his homeland and ultimately joined the popular V-8 Supercar series in the mid-'90s.

John Oreovicz covers motorsports for ESPN.com.