MELBOURNE : Top seed Iga Swiatek was bundled out of the Australian Open fourth round on Sunday, with title threat Coco Gauff also exiting in tears, as a pair of underestimated Grand Slam champions tore open the women's draw.World number one Swiatek was sent packing by Elena Rybakina in the early match at Rod Laver Arena, the Pole falling 6-4 6-4 to the Kazak Wimbledon winner who started her tournament in the Melbourne Park wilderness of Court 13.Rybakina shrugged off the scheduling snub before the fourth round showdown but used it as fuel in her first appearance on centre court as a tightly wound Swiatek slowly unravelled."I felt the pressure, and I felt that I don't want to lose instead of I want to win," said Swiatek, who dominated last season with two Grand Slam wins."I felt like I took a step back in terms of how I approach these tournaments, and I maybe wanted it a little bit too hard."Rybakina, the 22nd seed, might have expected to face Gauff in the quarter-finals but the much-hyped American teen was upset 7-5 6-3 by Jelena Ostapenko, the forgotten Grand Slam winner of women's tennis.The 2017 French Open champion thrashed 30 winners past Gauff on Margaret Court Arena, her last two sealing the match in style to leave the 18-year-old in tears at her post-match media conference."I feel like it was rough," Gauff told reporters, before breaking down with emotion."When you play a player like her and she plays really well, it's like, you know, there's nothing you can do."The win secured a first Australian Open quarter-final for hard-hitting Ostapenko, as well as the first at a Grand Slam since her run to the Wimbledon semi-finals in 2018.Latvia's first - and only - Grand Slam champion stunned the world when she hoisted