Qualifier Osorio stuns Garcia at Italian Open
On a soaking day in Rome, qualifier Osorio almost broke down in tears after her shock straight sets victory over Garcia, a two-time doubles winner at the French Open.
A career-best win for world number 100 Osorio puts her in the last 16 of a WTA 1000 event for the first time in her career.
She will face either Beatriz Haddad Maia or Magda Linette in the next round.
"I literally have no words to describe what I'm feeling right now," said Osorio on court.
"I've been struggling a little bit with my injuries and now that I'm back playing and beating the number four in the world I can't believe it.
"I'm just super happy and proud about how I managed to stay calm and finish the match."
Garcia joins world number two Aryna Sabalenka, third-ranked Jessica Pegula, 2019 winner Karolina Pliskova and world number seven Ons Jabuer in being dumped out of the tournament.
Osorio prevailed in a match which started two hours late and was interrupted for more than an hour at the start of the second set due to the pelting rain which covered the Italian capital for much of the early part of the day.
Only one match had been completed by the time Garcia and Osorio went back out onto the court at around 3.15 local time (1315 GMT), Andrey Rublev seeing off 6-3, 6-4 in the men's draw.
Carlos Alcaraz makes his Rome debut against fellow Spaniard Albert Ramos-Vinolas knowing that just playing the match will return him to the top of the men's rankings.