Katie Boulter secured an impressive 3-6 6-3 6-3 comeback victory against Antonia Ruzic to book a place in the Japan Open semi-finals and reclaim her title as the British No 1.

Boulter got off to a worrying start in a 34-minute first set, unable to wrangle momentum back after losing the first three games of the match in succession and eventually losing 6-3.

The Leicester native, though, showed resilience in the second set, breaking Ruzic's serve three times in a row to force a decider. She trailed 2-0 after being broken in her opening service game, but fought back superbly to level the match.

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The world No 58 was then buoyed, winning three games in succession to open the third set and surviving a late Ruzic break to win the final set 6-3 and secure safe passage into the last four.

The result also confirmed her reinstatement as Britain's best female tennis player, just five days after she ceded that mantle due to Sonay Kartal's run to the Wuhan Open final.

Boulter's progress in the tournament overturned her 55-point deficit in the rankings and dethroned Kartal back to the No 2 spot.

"[Ruzic] is a really good player," Boulter said of her opponent in her on-court interview on Sky Sports. "She's extremely tough to beat.

"I did extremely well to come back into it in the second set but she was swinging at everything hard. I felt like anything that I was giving her wasn't bothering her. Full credit to her.

"I tried to hang tough, and in the end I started to play a bit better. I was lucky in the second set, but in the end I felt like I did well to stay there."

Boulter will face Czech Katerina Siniakova in her semi-final match, live on Sky Sports on Saturday.

"[Siniakova is] one hell of a player - she's extremely dangerous," Boulter added. "I know exactly what she's going to bring to the table.

"It's going to be a great match - I've got nothing to lose and I'm going to come prepared tomorrow."