Flavia Pennetta, the 2015 US Open champion, has launched a surprise attack on Emma Raducanu's against-the-odds New York triumph, claiming it "could never have happened" in her day.
The Italian, now 39, cited the 18-year-old's sensational success as a qualifier in New York as evidence that "there is something wrong" at the highest level in women's tennis.
Pennetta became the first high-profile player to question the merits of Raducanu's success when she was asked in an interview whether she welcomed the variety of four different winners at the Grand Slam tournaments this year.
"I do not like it," she told the Corriere della Sera website, adding that the "very strong discontinuity" of winners "is not good for tennis".
Watch: Lunchtime Lessons - Find your balance with our easy desktop yoga home workout
"In my day it could never have happened that a girl who started from qualifying, like Emma Raducanu in New York, won a Grand Slam," she added. "Top athletes made too much difference. There is something wrong. Charisma is missing, so women's tennis is more difficult to sell."
Pennetta was seeded 26th when she won the US Open, beating fellow Italian Roberta Vinci in the final. Raducanu was ranked 150th in the world before her own American triumph.
Reflecting on her lengthy career in professional tennis, she suggested it was unclear whether Raducanu and Leylah Fernandez could enjoy long periods of success in the sport. "The very young Raducanu and Fernandez - it is all to be shown that they are confirmed," she added.
Referencing Serena Williams, she said: "A slam Queen cannot vanish into thin air. I have never been among the superstars but I lasted 15 years at a high level, and Francesca Schiavone [is] the same."
Raducanu, who was this week confirmed as the new face of fashion brand Dior, lost her opening match at Indian Wells after her victory at Flushing Meadows. However, Pennetta is alone in expressing views that her US Open win was bad for the sport.
Briton Cameron Norrie, who followed up her success by winning at Indian Wells, said this week that he had been inspired by Raducanu’s feats. "What Emma did in New York was amazing and tremendous for British tennis and is definitely going to inspire younger girls and boys to pick up rackets and play," he said.
"It just shows all those girls who are around that ranking, Harriet Dart [the world No 134] and Jodie Burrage [No 222], that they could qualify and go deep. What Emma has done has been extremely impressive and she inspired me a little bit."
Having parted company with her coach after the US Open, Raducanu last week lined up a trial with seasoned Spaniard Esteban Carril ahead of her planned return to competition at the Transylvanian Open in Romania.
Carril – who is 44 and had a highest singles ranking of No 462 – made his name by helping Johanna Konta climb from outside the world’s top 100 into the top 10, thanks partly to her unexpected run to the semi-finals of the 2016 Australian Open.
Raducanu’s year has already featured two relatively short-term coaching appointments. Nigel Sears filled the role during the grass-court season and Andrew Richardson during her six-week summer stint in the United States, which ended with her extraordinary triumph at the US Open.
She is entered into two more events this season, first in Romania in the coming days and then in Linz early next month.
Watch: Lunchtime Lessons - Stretch our your hands with our easy desktop yoga home workout