On the final point of her quarter-final win over Donna Vekic in San Diego last week, Katie Boulter was scrambling. She was dragged from sideline to sideline, lunging at every ball, desperately trying to stay in the point. After 24 brutal groundstrokes between them, Boulter chased down a drop shot, which she brushed aside with a searing forehand winner to close out the victory.

A year ago, it would have been difficult to imagine Boulter winning such points against top opposition. While the potency of her serve and clean, vicious groundstrokes have never been in doubt, whenever she was forced out of position at the highest level, her defensive weaknesses were laid bare.

The way she closed out Vekic, though, was symbolic of the continuous growth that has afforded the 27-year-old by far the biggest achievement of her career. On Sunday she finished an incredible week in San Diego by defeating Marta Kostyuk 5-7, 6-2, 6-2 to win her first ever WTA 500 title. Boulter now sits at No 27 in the WTA rankings, having risen from her previous career high of No 49. She heads to Indian Wells, one of the biggest events on the calendar, inside the top 30 and categorically one of the best players in the world.

Boulter’s rise is testament to her perseverance and patience. It has already been around five years since she broke into the Top 100 and began to compete on the WTA Tour before promptly suffering the misfortune of a stress fracture in her back. She was forced off the tour for seven months, falling back out of the Top 100 and as low as No 441 in February 2020.

More injuries followed and even when she finally began to rise the rankings again, she became stuck in the 120-200 ranking bracket, unable to bridge the gap. Boulter would rise to the occasions of Billie Jean Cup ties or when receiving wildcards to WTA events in Britain, but struggled to string together sufficient victories on the ITF circuit. Her surprise WTA title run at Nottingham last year, where she received a fortunate draw and showed her mettle by snatching the opportunity with both hands, proved to be a turning point in her career.

Since then, Boulter has been quietly impressive. There had been no spectacular result until this week, but she has been tidy, consistently beating lower-ranked opponents and testing her strength against the best. Finally able to compete exclusively on the WTA Tour for an extended period, performing at the highest level every week has provided countless lessons. After so many injury issues throughout her career, she has also learned how to manage her body, investing in a personal physio, Rory Mee, and adjusting to the rigours of the gruelling tour.

Having already risen 100 ranking spots last year to break into the top 50, Boulter’s mindset has been particularly impressive. She could have been entirely satisfied with her progress, but she was convinced that she had not yet come close to achieving the goals she had set for herself. “No matter how happy I might be with my year, I actually think it fuels me even more and makes me hungrier going into next year,” she said after her final match last season. “It’s given me a lot of belief that I belong at this level and I genuinely see and think that I can climb up the rankings.”

From her first tournament of the year at the United Cup, where she defeated the world No 5 Jessica Pegula, Boulter showed that she was ready to convert her learnings into winning tennis. She had never previously beaten multiple top-50 opponents in a single tournament, yet in San Diego she defeated five in a row, including a win against the No 13-ranked Beatriz Haddad Maia, her fourth career win against a top-20 player.

Alongside her improved movement and physical resilience, the British No 1 has worked with her coach, Biljana Veselinovic, to strike her potent groundstrokes more thoughtfully, now using the angles to open up the court effectively instead of playing more linear tennis. After enduring so much just to reach the top levels of the sport, Boulter is playing with a level of freedom that makes her particularly dangerous.

As Boulter accepted the biggest trophy of her career on Sunday night, she recognised the efforts of her boyfriend, Alex de Minaur, who was watching from the stands. A day earlier, De Minaur defeated Casper Ruud 6-4, 6-4 to win an ATP 500 title in Acapulco before flying to San Diego in the early hours of Sunday morning. Both players have started the year producing the best tennis of their careers while clearly pushing each other on, and it will be fascinating to see how high they can go.

• This article was amended on 5 March 2024. Katie Boulter is not seeded for the Indian Wells tournament as an earlier version said.