Lopez's hopes for gold in London disappeared in an instant on Thursday when she fell 1-0 in overtime to two-time world champion Hou Yuzhuo of China. After almost seven scoreless minutes, one well-placed kick was the only point of the bout.
"I felt stronger than her," Lopez said. "I just went off the line, and she tapped my chest protector. That's it."
The electronic scoring system flashed -- fighters wear vests with sensors to determine whether kicks are worth a point -- and Hou raised her arm in celebration. Lopez left the mat with a stunned look on her face. Her coach and brother, Jean Lopez, stood up to greet his sister, then stared blankly ahead.
It was a far cry from how they entered the arena about 10 minutes earlier, Diana Lopez smiling and nodding as she walked toward the mat, Jean Lopez a step behind her and confidently holding his right fist skyward.
"I've seen her fight before," Diana Lopez said of her opponent. "Nothing spectacular. She's not a front-leg fighter, which is even better for me. I could have let go a little bit more."
She added: "I was hesitant because I knew she liked back kicks. My brother told me to wait and just hit on her motion when she came in, but she was waiting for me, so we were waiting for each other. And I couldn't believe that registered. I'm still in shock."
Diana Lopez was a bronze medalist at the Beijing Games four years ago. She still could compete for bronze later Thursday in London, depending on how far Hou advances in the bracket. Hou's next match is a quarterfinal Thursday against Suvi Mikkonen of Finland.
The London Games are the first to use electronic body protectors that automatically record kicks and punches delivered with enough force. Head kicks are still scored manually.
"I didn't know what was going to score, what wasn't going to score," Diana Lopez said. "I felt there were some points defensively where I kicked, and nothing registered. That's the way an electronic scoring system works."
Diana Lopez's brother, two-time Olympic champion Steven Lopez, fights Friday in the under-80-kilogram division. At least one member of the Lopez family won a medal at each of the previous three Olympics, starting with the Sydney Games in 2000.
Much like his sister, Steven Lopez has a tough draw awaiting him.
Steven Lopez, the Olympic gold winner in 2000 and 2004 and a bronze medalist from 2008, opens his schedule in London against reigning world bronze medalist Ramin Azizov of Azerbaijan -- the No. 1 seed.
Hou and Diana Lopez went through three scoreless two-minute periods, both seeming to play plenty of defense against the other, urged by occasional yells of "fight" from referee David Coupar of Denmark.
In the end, all Hou needed was one opportunity.
"I was just standing still waiting for my opponent to attack me first," Hou said. "And then I hit her, scored the only point I needed to win."