Japanese champion Akifumi Shimoda was stunned by American challenger Rico Ramos in the seventh round Saturday, suffering a knockout that cause him to fail in his first defense of the WBA super bantamweight title.

The 26-year-old Shimoda was attempting to defend the WBA crown he wrested from Retsuri Lee on Jan. 31. He was making a bid to become only the third Japanese champion to defend a title overseas.

Although trailing on the judges' cards, the undefeated Ramos landed a devastating left hook to the temple after 2 minutes, 46 seconds of the seventh that sent Shimoda crumbling to the canvas.

"I think I got a little flustered. I was thinking too much about this being my opponent's backyard," said Shimoda. "I should've been more composed. It's really disappointing. I'd like another shot if possible."

Shimoda, who controlled the pace wracking up points on body blows through the first six rounds, slipped to 23-3, including 10 knockouts, with one draw, while Ramos improved to 20-0 (11 KOs).

"The first five rounds he was frustrating me, and I knew I couldn't allow that to happen," said Ramos. "I wasn't looking for a knockout. I just knew I had to move forward and carry the fight."