Johnny Herbert believes conquering the physical side of Formula One will be Michael Schumacher's biggest challenge on his return to the sport.

Herbert, who won three times in an 11-year F1 career and was Schumacher's team-mate for Benetton in 1995, is confident, however, the 40-year-old will make a success of his comeback after he agreed to replace stricken Ferrari driver Felipe Massa.

"I think he'll find it hard work. The last time he drove an F1 car was in 2008", Herbert told Radio 5 Live.

"The difference is the power behind the car. For a human to jump back into something such as an F1 car is going to be immensely difficult for him.

"When you are at full fitness and testing every week, you are honing your body and the muscles, especially the neck muscles, build up with that.

"You can train away from it for sure but you get that little bit more when you drive the car and he hasn't done that. This is completely different and he only has four weeks to get back in condition."

Reaction to Schumacher's return has been mixed but Herbert believes the German - a seven-time world champion - has "everything to gain".

He added: "There are all these negatives about it but I am sure he has taken it all on board.
"I don't think he has anything to lose, everything to gain.

"Ferrari haven't won this year. If Michael Schumacher comes out and wins a grand prix he will be the biggest god in Italy. It will be awesome if he is able to do that."