Ronda Rousey is in the running for the toughest woman on planet earth, but there is one opponent who can make the undefeated mixed martial arts star "weak at the knees."

No, it's not a fellow UFC opponent like Holly Holm, Cat Zingano, or Miesha Tate. It's Antonio Banderas.

Ronda Rousey Reveals Her Male and Female Sports Crushes

Rousey and Banderas both appeared in the third installment of Sylvester Stallone's Expendables trilogy, and "Rowdy" was reported "overawed" by the Spanish actor during one particular scene that required Banderas to hold Rousey in a "precarious position." A full report of the star's swoon can be found at The Sun. Rousey was quite the hit on the film's set. No, literally -- she reportedly broke director Patrick Hughes' rib while training for a fight scene.

Get Ready for a Ronda Rousey Memoir in 2015

Rousey's next fight in the octagon is coming on February 28 of 2015, in Los Angeles. She'll defend her bantamweight title belt against Cat Zingano as a co-main headliner of UFC 184.

Ronda Rousey Next Fight: Title Defense Against Cat Zingano Set

You can watch The Expendables 3 trailer below, now available on DVD and Blu Ray. Rousey's cameo comes at the 0:53 mark: