“If Rudiger leaves, it would be a real pity for Chelsea,” Petit told bookmakers.co.uk.
“If I remember correctly before [Thomas] Tuchel came in he was on the bench and wasn’t playing. Now he looks like one of the best defenders around.
“He could leave on a free and Chelsea would have to spend a minimum of £30m to find a new defender of his level, and there’s never a guarantee a buy will work out.
“If he asks for two more years, just give him the money.
“This guy is a survivor. Since Tuchel has been the manager he’s been one of the top defenders in world football.”
Rudiger has been a mainstay in Chelsea’s line-up since Tuchel’s arrival, racking up 15 appearances already this season as well.
As a contributor to the league’s best defense, his competitiveness and ability will be difficult to replace at Stamford Bridge.