The 18-year-old played her first match since her victory at Flushing Meadows, winning the opening match but then struggling against the world number 100 Sasnovic.
Nou told reporters after her 10-game winning streak ended.
“During the match I didn’t put pressure on myself because in my mind I am very inexperienced. I am 18 years old. I need some slack.
“You can tell she was more experienced than me and went out there and executed her game plan better than she did.”
Sasnovic scored 17 wins and 9 negative fouls, while Radocano scored 31 unforced errors.
“I’m really enjoying playing here,” said Sasnovic, who will now face Simona Halep. “Emma just won the US Open and lost there in the first round. So it was a little different.”
Raducanu won the US Open in an extraordinary race in which no group fell.
Raducano said she is now looking for a more experienced coach and at Indian Wells she has worked with senior women’s national team coach Jeremy Bates.
“Jeremy is part of the women’s tennis in the association, so while he’s here he’s helping me,” Radocano said.
“Going forward, I will wait and try to find the right person.”
Raducanu became the first-ever qualifier – a man or a woman – to win a Grand Slam title, having entered the tournament at number 150 in the world.
“I am happy with what happened today so that I can learn and take it as a lesson,” said Radocano. “She’s got more experience than me. She’s been 4-2 hundreds of times behind.
“It’s my third WTA tournament this year. Just don’t be in a hurry and get my head back on the drawing board.”
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