Coco Gauff demonstrated her trademark resilience and tenacity as she fought back from a set down to knock fourth seed Jessica Pegula out of Wimbledon and reach the semi-finals for the first time.Pegula, the highest seed left in the quarter-finals, broke Gauff in the first game and held the upper hand throughout the first set.But she was left to rue her failure to take chances and general passivity in the second and third as seventh seed Gauff fought back, winning 4-6 6-3 6-3 in an hour and 48 minutes.The two-time grand slam champion, who made her breakthrough at Wimbledon as a 15-year-old in 2019, grew increasingly confident as she tightened up on serve and minimised her errors.Having hit four double faults and 17 unforced errors in the first set, she leaked just three more double faults and 15 unforced errors over the next two. Meanwhile Pegula paid the price for two dire service games, at 3-4 in the second set and at 3-3 in the decider, when she was broken to love twice and unable to recover. Gauff grinned up at her box and appeared to say, “Oh my God, how?” as she clinched victory as Pegula dumped the ball into the net, and said on court: “Honestly pretty insane [to make the semi-finals], considering I hadn’t won a match on grass in two years before this tournament! Really happy with how I played today, Jess is an incredible opponent and person and playing against her is never easy. “In the first set I made too many errors, rushing the rallies too quickly. I just felt the last two sets were really great tennis. I’ve gone to three sets in the last few, [you have to] have that faith in yourself when the match goes the distance, when you lose the first set you’re not panicking.”Gauff is into the Wimbledon last four for the first time (AP)Gauff has now won four three-set matches in a row, including a thriller against 11th seed Belinda Bencic in the fourth round when she clinched victory with two minutes before Wimbledon’s curfew set in.Having never previously gone beyond the fourth round at SW19 she appears to have found her rhythm on grass, or at the very least converted her trademark ability to grind out wins on hard and clay courts onto the surface. Asked how she deals with the expectations placed on her after her breakthrough here six years ago, when she beat Venus Williams to reach the fourth round, she said: “Maybe some people, I think a lot of people had me going out in the first or second round! I’m just happy to get to the semis. I didn’t feel nervous, I don’t know if I’m becoming a vet, or…”Gauff will play the winner of 14th seed Naomi Osaka and 10th seed Karolina Muchova, who play later on Tuesday, in the last four.