Emma Raducanu was forced to retire from her Korea Open quarter-final against Daria Kasatkina due to a fresh injury problem.

The 21-year-old lost the first set 6-1 against the top seed but was evidently struggling with a foot issue throughout the opener, and she called it quits before the second set got underway.

Raducanu had previously needed treatment on her foot in her second-round win over China's Yue Yuan, but she came through that straight-sets victory ostensibly not suffering from any major injury.

The former US Open champion was then given more time to recover as inclement weather forced the postponement of the quarter-finals, originally scheduled for Friday, and she asked questions of the Kasatkina serve early on despite her problem.

Raducanu brought up two break points in Kasatkina's opening service game, although she failed to take either of them before losing serve herself, falling 2-0 down to the top-seeded Russian.

Raducanu all smiles despite Korea Open injury

However, the 21-year-old fought fire with fire as she immediately broke back to 30, although she had only poked the Kasatkina bear as the world number 13 won the next four games on the spin to convincingly wrap up the first set.

Raducanu's serve - which she has been making major adjustments to in recent weeks - was hampered by her foot problem, although she still managed to threaten Kasatkina on the returning side, bringing one break point in each of the Russian's last two service games.

Kasatkina quickly closed the door on the former British number one, though, and Raducanu then retired after just 32 minutes, although she was all smiles as she chatted to Kasatkina after the short-lived battle.

"First of all, I feel sorry for Emma for retiring during the match. It's a pity to get injured, especially in the deeper stages on the tournament. I wish her a speedy recovery to get ready for the next tournament. I know that this swing is important for her," Kasatkina said on the court.

Despite her fresh injury blow - the severity of which is unclear - Raducanu still enjoyed a positive week at one of her favourite tournaments, defeating two top-50 opponents in Yuan and Peyton Stearns to earn a match with Kasatkina.

The top seed - who is now 3-0 in matches against Raducanu - will meet either Diana Shnaider or Marta Kostyuk in the Korea Open semi-finals.