Melbourne: World No.4 Agnieszka Radwanska survived an inspired performance from No.82 Anna-Lena Friedsam, winning 6-7(6), 6-1, 7-5 in a see-saw fourth-round thriller lasting more than two and a half hours at the Australian Open tennis tournament here on Sunday. The two have played once before - earlier this year in Shenzhen where Poland's Radwanska eased to a straight sets victory. But despite that result, Radwanska knew German Friedsam was bound to be a tough Round of 16 opponent. "We just played two weeks ago and I knew it was going to be a tough one," Radwanska said post-match. "She's definitely playing better than her ranking, and definitely, she was playing amazing today." The two stayed tight and pushed the first set into a tiebreak, where they stayed dead even until Friedsam blasted a forehand volley that left Radwanska wrongfooted, sealing it at 7-6(6). Radwanska shook it off, though, and rushed to a 2-0 lead in the second set as the wind seemed to leave Friedsam's sails. Radwanska was too good, making only two unforced errors and needing just 26 minutes to wrap up the set 6-1 and level the scoreboard. In the final set, Radwanska came out again with a 2-0 lead and it looked like the World No.4 had the match in the bag. But the 21-year-old refused to fold, rallying back to win the next five consecutive games to get a 5-2 lead, leaving Radwanska to serve to stay in the match. Radwanska rallied back to bring the score to 5-5. Ultimately, the intensity of the long match took a toll on Friedsam, who struggled physically as Radwanska grabbed the next two games and closed out the match 6-7(6), 6-1, 7-5. Radwanska's next opponent will be No.10 seed Carla Suarez Navarro, who beat Australian Daria Gavrilova, 0-6, 6-3, 6-2.