Alexander Skarsgard thinks Riahnna is a hard worker.

The 'Battleship' actor claims that when he worked with the 'Where Have You Been?' singer on the movie, he was impressed with how she juggled her career in entertainment.

He told Bullett magazine: ''God, I thought I worked a lot. We would shoot until late Friday night and she would jump on a plane and go to L.A. to perform at the MTV Video Music Awards in front of a billion people, and then get straight back on the plane and fly to Hawaii, and go to set Monday morning with a smile on her face.''

When he is not appearing in his ongoing role as Eric Northman in vampire TV show 'True Blood' the 35-year-old admits her likes to keep his work varied by appearing on the big screen with stars such as Taylor Kitsch, Liam Neeson and Brooklyn Decker, for Example.

He continued ''I spend seven months just playing Eric on 'True Blood'. But when I'm on hiatus, when I get my five months off, I'm not looking to play the same character again.''