Damon Hill has warned Michael Schumacher to expect an 'unpleasant' return to Formula One.
Whilst the sport's supremo Bernie Ecclestone is anticipating a 'jaw-dropping season' in 2010, former world champion Hill feels it will not all be a bed of roses for the seven-time king on his comeback.
Schumacher last week ended three years in retirement by signing a 20 million pound, three-year deal with Mercedes GP.
Despite his many titles and records, Schumacher was also renowned for his controversial side, one of which led to his first crown in 1994.
Hill missed out on the championship by a point, accusing the German of deliberately causing a crash in the final race of the season in Adelaide that forced them both out.
Hill, who went on to take the 1996 crown, believes the 40-year-old will arguably now face the sternest examination of his glittering career.
"At some point the season is going to get very tough, going to get unpleasant and it might bring back memories of why you retired in the first place," Hill told Schumacher on BBC Radio 5 Live.
"We'll have to see. A season is a long time and it will put Michael through a severe test of his ability."
Hill also feels world governing body the FIA will need to be whiter than white should Schumacher fall foul of the law, in particular as his close friend and former Ferrari team principal Jean Todt is now the president.
"There's going to be a lot of interested viewers watching the sport for that one, because the suspicion was always that Michael got a little bit of favouritism from the FIA," added Hill.
"I think the FIA are going to have to be on their toes to make sure there is no suspicion of that in the coming season."
Schumacher's return has at least fanned the flames ahead of what is certain to be one of the most enthralling seasons in F1 history.
Ecclestone, for one, cannot wait as he said: "It is fantastic for Formula One that he has turned into a comeback kid."
"But at the same time it's good for Michael. When drivers have put in many years they sometimes lose focus and motivation - probably that was one of the reasons for his retirement in 2006."
"But now he has again put all his strength together and has a 100 percent motivation level that will give us many exciting races in 2010."
"I always said Formula One is a strong brand. It has demonstrated time and again it can pull itself up by its own bootstraps."
"All indications point to a jaw-dropping season. Fans will love it."
Despite his time away from sport, and the fact he will turn 41 on January 3, Ecclestone has no doubt Schumacher can go on to add to his record haul of titles.
"Forget about winning races - I have him on my bill for winning the championship," exclaimed Ecclestone.
The sport itself, at the end of a turbulent year that almost saw it torn apart by a civil war and with two further manufacturers opting to withdraw in BMW and Toyota, will also benefit enormously.
As Ecclestone remarks, the sport needs characters, with Schumacher one of the most charismatic, as well as controversial.
Asked if this was again the time for characters in F1, Ecclestone replied: "There is no doubt about that."
"Michael, as we all know, was and is one of the most outstanding characters F1 has ever created."
Schumacher's wife Corinna, meanwhile, has confirmed she is firmly behind her husband's return, despite admitting it will turn their 'family life upside down'.
"When he told me (Mercedes GP boss) Ross (Brawn) had called, I immediately felt he was on fire again," remarked Corinna.
"As a matter of fact, Michael's passion for racing is enormous and without this deep passion all that would not have been possible. This passion made Michael who he is today."
"He knows exactly what he's doing, and he knows as well that I'm always supporting him."
"Michael simply needs challenges. That's just the way he is. I can really understand his decision and, to be honest, I actually think it's great."