World number nine Jo-Wilfried Tsonga suffered a shock exit in the first round of the Rio Open, beaten 6-3 3-6 6-4 by wildcard Thiago Monteiro on his ATP World Tour debut.
Monteiro sits 329 places below the Frenchman in the world rankings but earned a stunning victory in his hometown to advance to the second round.
The 21-year-old Brazilian won 13 of a possible 16 points off his first serve, and five from seven on his second, as he powered into a first-set lead.
Number three seed Tsonga responded with a string of powerful service games that included four aces to force a decider.
However, the Frenchman made three double faults and Monteiro secured the only break of the set to send the home crowd into delirium.
The world number 338 will now face Uruguay's Pablo Cuevas in the second round.