The Brazilian-born Italy international moved to Stamford Bridge last month, having been heavily linked with Premier League champions Manchester City.
He has been joined in west London by his former Napoli boss Maurizio Sarri, who replaced Antonio Conte.
And former Real Madrid and Juventus striker Morata feels Jorginho will prove to be a key acquisition as the Blues, champions in 2016-17, seek to improve on a disappointing fifth-place finish in the league last season.
"We are lucky," he told the Mirror.
"We've made a very good signing, because he's a fantastic player, a fantastic guy and because Manchester City wanted him! It would have been very bad for us if City has taken him.
"He was one of the best signings of the last year for Chelsea because now, when we have the ball, he is the key.
"Jorginho and Cesc Fabregas with the ball are two of the best midfielders around.
"There are not too many midfields with this level with the ball - for the strikers it is fantastic."
Morata has also been wowed by teenager Callum Hudson-Odoi, who has been tipped to break into Chelsea's first team during the campaign ahead.
"I have never seen a player like him," the Spain international said.
"Ethan Ampadu and him, when you see them playing, it is like they are 25 and 26 years old - and they are 17! They work so hard.
"Callum is lucky with Eden [Hazard], with Willian and all the strikers because they are good people and if he listens and watches Willian, he can be the best for the future."