Several top seeds were pushed to the brink on day five at the <a href="https://www.thenationalnews.com/tags/australian-open/" target="_blank">Australian Open</a> as top-ranked woman Iga Switaek admitted she was "at the airport already", while on the men's side, Alexander Zverev and Casper Ruud were taken to five sets in their second-round matches. Four-time Grand Slam champion <a href="https://www.thenationalnews.com/tags/iga-swiatek/" target="_blank">Swiatek</a> staged an astonishing comeback against American Danielle Collins to win 6-4, 3-6, 6-4. The Polish world No 1 looked to be cruising when she led by a set and a break but soon found herself 4-1 down in the decider, with Collins serving to make it 5-1. Switaek then reeled off five straight games to survive a major scare and extend her winning run to 18 matches. "Oh my God, I was at the airport already," Swiatek, 22, said jokingly. "I wanted to fight until the end. I knew she played perfectly but it would be hard for anybody to keep that level, so I wanted to be ready if the mistakes would come from the other side. "It wasn't easy. I felt like I had the momentum going and then she started playing suddenly two times faster and I had no idea how to react to that for a couple of games. I came back, and I thought the only thing I could focus on was myself." Swiatek, who will face unseeded Czech player Linda Noskova in the third round, reeled off 36 winners against 35 unforced errors. But despite her dazzling comeback, she will know that she has to move up a gear and find more consistency if she is to go deep and capture her first Australian Open title. After the match, former finalist Collins announced that she would be retiring at the end of the season. “This is going to be my last season, actually, competing,” the 30-year-old American said. “I don’t really know exactly when, but this will be my last season and I’m really looking forward to that.” On a dramatic day at Melbourne Park, sixth-ranked Alexander Zverev and Casper Rudd, the 11th seed, were pushed to the brink before both came through their matches in fifth-set tie-breaks. Facing a second consecutive second-round exit in Melbourne, Germany's Zverev came back to win 7-5, 3-6, 4-6, 7-6, 7-6 after a gripping contest lasting four-and-a-half hours on Margaret Court Arena. "A lot of the times I was a spectator in the match," Zverev, 26, said. "I was just, you know, witnessing whether he's going to hit a winner or miss. "That's not a nice feeling to be in, especially in the important moments, but I'm happy that I managed to win." Zverev faces Alex Michelsen next after the unseeded American teenager upset Czech 32nd seed Jiri Lehecka. It was a similar story for three-time Grand Slam finalist Ruud, who was taken to a deciding set by Australia's Max Purcell, which he won 10-7. Ruud thought his match against the unorthodox Purcell was one he might have lost before the boost of confidence he got from a fine showing at the year-opening United Cup. "That's a typical match you could end up losing," he told reporters. "Today I didn't have to save match point, but he was basically only three points away from winning. It might be the good start I had in United Cup that gave me some confidence to stay in the rally and play well when I had to." The Norwegian will next meet British 19th seed Cameron Norrie, who came back from two sets down to beat Italian qualifier Giulio Zeppieri. Carlos Alcaraz said he reached a "great level" as he booked his ticket for the third round on Thursday. The Spanish world No 2 matched his best Melbourne result by reaching the last 32 with a 6-4, 6-7, 6-3, 7-6 win against Italy's unseeded Lorenzo Sonego. The two-time major champion, who struck 43 winners on Rod Laver Arena, found himself all square at one set apiece despite not facing any break points in the first two sets. But he brushed off the loss of the second set, breaking early in the third set, and came out on top in the fourth-set tie-break in windy conditions. Alcaraz will meet Chinese wildcard Shang Juncheng next as he ramps up his drive towards a maiden title in Melbourne. "I'm really happy with my performance today," said the 20-year-old. "I think both of us played such a great level, high intensity. "Even if I lost the second set, I think I played a good game. We put on a show, both of us, making good points and some hot shots as well. It was a great match." Alcaraz, who missed the 2023 Australian Open due to injury, is aiming to become the third man in the Open Era to win three Grand Slams before the age of 21, after Bjorn Borg and Mats Wilander. He also has the chance to supplant Novak Djokovic as world No 1.