LONDON, June 30 (Reuters) - Second seed Aryna Sabalenka showed exceptional grit to rally from a set down to beat British wildcard Katie Boulter in a thrilling match on Wednesday and reach the third round of Wimbledon for the first time. Sabalenka"s best result at the grasscourt Grand Slam was a second-round showing on debut in 2017 as a qualifier but she bettered that with a 4-6 6-3 6-3 victory in a match lasting over two hours. The withdrawal of Naomi Osaka and Simona Halep from the tournament, which was cancelled last year due to the COVID-19 pandemic, meant world number four Sabalenka was at her highest seeding in a major. Boulter had lost in straight sets when she met Sabalenka in their only meeting at the same stage of the 2019 Australian Open but this time she came armed with better tactics, denying her opponent pace on the ball. Boulter repeatedly played the short slice to draw Sabalenka to the net only to lob her, much to the delight of the Centre Court crowd. After an early trade of breaks, Boulter consolidated a second break of serve for a 5-3 lead as Sabalenka made errors with her ultra-aggressive approach. The 23-year-old Belarusian cut a frustrated figure, shrieking in anguish as she failed to convert her chances and the crowd got behind the home favourite. Sabalenka did manage to limit her mistakes, however, and a lone service break in the second set after a Boulter double fault was enough for her to level the match at 1-1. Sabalenka broke early in the final set before Boulter took a medical timeout for treatment on her right elbow. The 24-year-old, who reached a career-high ranking of 82 in 2019 but has endured injury problems, returned to the court and broke her opponent"s serve to love. Sabalenka broke back immediately, however, and consolidated her advantage to take a 4-2 lead. Boulter had six chances to break back in an eighth game lasting nearly 11 minutes but Sabalenka saved them all with massive first serves. The Belarusian, who will next meet either Russian Ekaterina Alexandrova or Colombian qualifier Maria Camila Osorio Serrano, converted her first match point and let out a huge roar in celebration.