Moscow, Jul 27 (IANS/RIA Novosti): Spain suffered a surprise defeat in their Olympic football opener Thursday, going down 1-0 to Japan and having a man sent off.

Yuki Otsu was the hero for Japan at the match at Glasgow's Hampden Park, beating Spanish goalkeeper David de Gea with a strike on 33 minutes before Inigo Dominguez picked up a straight red card for a foul on Kensuke Nagai nine minutes later.

Japan could have sealed their win with a breakaway goal on 86 minutes, but De Gea managed to block Nagai's low shot, before Hotaru Yamaguchi hit the ball over the bar in stoppage time as Spain's desperate attempts to equalise left them open at the back.

The world and European champions had started brightly, with Chelsea midfielder Juan Mata their main creative outlet, but struggled to break down a compact Japanese defence, even before having Dominguez sent off.

After the red card, Japan took control and restricted Spain's shooting chances while creating plenty of their own.

Spain's next match is against Honduras Sunday, before they play Morocco Wednesday.

Honduras and Morocco drew 2-2 in their opener Thursday.