In a pulsating contest, world No 46 Collins rallied from a set down to beat Raducanu 4-6, 6-1, 6-3 at the WTA 500 event.
It is just a second quarter-final appearance of 2025 for the American, who has struggled at times across 2025.
“I knew playing Emma that I would have to play my aggressive game style,” said Collins on court.
“The more that I did that, I think that I was able to kind of stay in control of the points and really push her. She played really and gave me some challenges – but I just kept going after it.”
Things started brightly for world No 43 Raducanu, who produced some superb tennis on her way to winning an impressive opening set.
However, while Collins improved notably after a shaky start, the Brit’s form faded badly and she ultimately called for the trainer.
Raducanu took an off-court medical time out for a back injury at 5-0 down in set two, though returned to court and managed to hold before Collins forced a decider.
The pair traded early breaks across a tense deciding set, though the US star ultimately broke in Raducanu’s final two service games to triumph.
Raducanu struggled with a back injury at the start of 2025, withdrawing from the Auckland Open ahead of the Australian Open.
The 22-year-old will hope that the problem is nothing too serious ahead of the second Grand Slam of the year at the French Open, which begins this coming Sunday.
Raducanu has not played at Roland Garros since 2022, withdrawing due to injury in 2023 and due to scheduling concerns in 2024.
Defeat for the Brit also means she has missed the chance to potentially return to the top 40 of the WTA Rankings post-event.
Raducanu is currently ranked 43rd in the world but is up to world No 41 in the WTA Live Rankings, following her opening-round win over Daria Kasatkina.
Victory against Collins would not have seen the 22-year-old rise any further up the rankings but, had she won, she would have then been just one victory away from a top-40 return.
