Stamper, a world bronze medallist in South Korea two years ago, lost out to little known Egyptian Ghofran Zaki in the -68kg weight division.
"I'm obviously totally devastated that I've lost in my first fight," said the 2013 German Open champion.
"I didn't know much about my opponent but he's really tricky and will cause trouble in this tournament.
"He's the tallest opponent I think I've ever faced and he was really awkward and played a good game.
"I thought I'd be a lot sharper than that in the fight which is very disappointing.
"I just didn't feel as good as I would have liked. There was nothing anyone else could have done, it was just the way I was feeling.
“I’ve had great preparation and have made sacrifices. Training and sleeping in an altitude tent for five weeks and then getting to Mexico early.
“But I just didn’t feel that I had it today. I wasn’t at my sharpest but to be fair he fought a great match and it’s as much down to that. It just wasn’t meant to be.”
Stamper's early elimination followed a battling performance by international Ruebyn Richards. The Nottingham prospect reached the quarter-finals before losing to home favourite, Uriel Adriano.
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