Pato has joined Stamford Bridge on loan from Corinthians until the end of the season, although he hasn't played a competitive game since November 28.
Guus Hiddink has admitted that Pato will need to improve his fitness before he makes his debut for Chelsea, while Wilkins, who has worked as an assistant to Luiz Felipe Scolari and Carlo Ancelotti at Stamford Bridge, believes the Brazilian's condition does not look promising.
"I don't know [if he's a good fit]. He was a superstar so young, then he went back to Brazil and we've almost lost sight of Pato," Wilkins told BT Sport.
"All of a sudden he once again reinvents himself coming to Chelsea. It's going to be interesting to see what sort of level he's at.
"I saw him coming through the airport the other day, he looked rather jowly, a bit chubby, so he might need to work a little bit hard, because our division is not that of Brazil.
"His jowls were slightly robust, so he might need a little bit of work before he gets in the side. But if he shows what he did for AC Milan at Chelsea, the fella will be a revelation."