British number one Katie Boulter emulated her compatriot Jack Draper as she reached her maiden WTA 500 semi-final with a two-set beating of Donna Vekic at the San Diego Open.

Only a matter of hours after Draper advanced to his first ATP 500 semi at the Mexican Open, Boulter bested seventh seed Vekic 6-4 6-3 in one hour and 36 minutes to break new ground of her own.

The world number 49 - who is set to break into the top 40 of the WTA rankings for the first time next week - had already laid down two markers by defeating Lesia Tsurenko and second seed Beatriz Haddad Maia before meeting Vekic at the top level for the first time.

Boulter had to do it the hard way at first, losing serve in the fourth game of the first set as Vekic established a 3-1 lead, but the British number one broke back immediately and also recovered from a 40-0 deficit in her next service game.

With the momentum swinging her way, Boulter broke for a 5-4 advantage before seeing out a hold to 30 to take the opening set, and the 27-year-old raced into a 4-0 lead in the second despite still being prone to the odd double fault.

Boulter failed to serve out the match at the first time of asking as Vekic earned one break back for 5-3, but the Croatian ceded a match point on serve in the ninth game, where Boulter emerged triumphant from a gripping 24-shot rally with a well-executed forehand.

"It was an absolute battle in tricky conditions, it was not easy to get any rhythm as we are both big hitters. I got over the line in the first set and played some good stuff in the second," said Boulter, who will face American third seed Emma Navarro in the final four.