Michu joined the Italian club on Thursday evening on a season-long loan from the Swans with an option to make the deal permanent next summer.
The former Oviedo and Celta de Vigo player struggled with injuries last season and scored only two goals in 15 starts in the Premier League.
"Michu is a player that can play in two positions," Benitez said in Friday's press conference. "He can play as a striker or as a lone forward.
"He is able to penetrate and score but also knows hows to play with other strikers.
"I have told Michu that I expect a certain number of goals from him just to motivate him but he first has to adapt to the team and get to know his new team-mates."
The Spaniard joined Swansea from Rayo Vallecano for £2.2million two years ago and was the club's top scorer with 22 goals in his first full season.
Michu is under contract with the Swans until June 2017.