London — Tournament favorites Spain have suffered one of the biggest upsets in Olympic football history, losing 1-0 to Japan at Glasgow's Hampden Park on Thursday.
Striker Yuki Otsu found the net in the 33 minute, thumping the ball home from a corner that found its way through a crowded penalty box.
Things got worse for Luis Milla's side as Real Sociedad defender Inigo Martinez was shown a red card minutes before half-time.
It was a harsh decision from American referee Mark Geiger, who sent off Martinez for apparently pulling down Kensuke Nagai as the two players ran towards the Spanish goal.
Spain's Olympic football squad had been expected to add Olympic gold to the country's already impressive collection of titles. The Spanish team recently won its second consecutive European Championship, to add to the 2010 World Cup won in South Africa. Spain also holds the European under 19 and under 21 titles.
The European champions enjoyed more of the ball throughout the 90 minutes, with Chelsea's Juan Mata the key figure in midfield.
However, they struggled to deal with the pace of Japan's attacks and David De Gea, Manchester United's young goalkeeper, kept his country in contention with several outstanding saves.
Japan, who upset the odds when they beat favorites Brazil at the 1996 Atlanta Games, could have extended their lead as Spain chased an equalising goal, but Nagai and Hotaru Yamaguchi both failed to convert easy chances.
Earlier in the day, Honduras and Morocco got the men's tournament underway with a 2-2 draw that leaves Spain bottom of Group D.
Abdelaziz Barrad opened the scoring for Morrocco, before Honduran forward Jerry Bengtson equalized with a close range tap in. Bengtson, who plays for New England Revolution in the U.S., then put his side ahead with a 65 minute penalty.
However, the lead only lasted two minutes, with Zakaria Labyad chipping the ball over Honduras goalkeeper Jose Mendoza in the 67 minute. Moments later Morocco's Zakarya Bergdich was sent off for kicking out at Mario Martinez, but the African side managed to hold on for a point.
Earlier, Mexico and South Korea got Group B underway with a goalless draw at St. James' Park, Newcastle. Substitute Raul Jimenez went closest for Mexico when he struck the post in injury time, with South Korean captain Jacheol Koo going closest at the other end with a glancing header.
It was a disappointing game between two sides with genuine hopes of making it to the knockout stages.