"I wish him the best of luck. I hope he can do the best thing for a footballer and that is to play football, now he can do that in a great side," Lippi was quoted as saying by Football Italia magazine on Wednesday.
"He now has five months to put himself into the spotlight in order to aspire to a World Cup place," he added.
Real Madrid signed Cassano on a four-and-half-year on Tuesday to put an end to his long contractual-dispute with Roma board.
Although no financial details were announced, Spanish media reported that Cassano will receive $6.54 million.
The 23-year-old featured rarely under the Azzurri coach due to his problems with Roma which kept him out of the capital side's squad most of the Serie A campaign.
The former Juventus boss stressed that Cassano's move outside the Italian Serie A won't have any effect on his chances of playing in the World Cup.
"I follow all players with the same amount of attention, even those ones who are abroad," he said.