Second seed Simona Halep survived a scare at the US Open by overtaking American wild card Danielle Collins 6-7 (2), 6-1, 6-2 in Monday’s opening center court match.

The French Open finalist moves on to face Slovakian Jana Cepelova, a 2-6, 7-5, 6-1 winner over Spain’s Maria-Teresa Torro-Flor, in the second round of the season’s last grand slam.

But the 22-year-old Romanian had a tricky time getting by Collins, a US college champion from the University of Virginia. Down a break at 3-4, the 20-year-old American brought the set back on serve at 4-all and with her confidence growing the collegian ran away with the decider by taking advantage of a slew of errors from Halep. That shock seemed to snap the Romanian back to attention, and bring her groundstrokes under control as she roared to victory over Collins, who was playing her first tour-level main draw match.

“She played a tough match, I want to congratulate her,” world number two Halep said in an on-court interview. “First set I was a little bit nervous. This court is huge. It’s my best ranking ever and best moment of my life. I have to enjoy it, but it’s not easy. Everybody is telling me I have chances to win this title.”

Halep, who broke through last season by notching her first six career tour titles, has two titles this season and finished runner-up to Maria Sharapova at Roland Garros in her first grand slam final.

Veterans show

Two 23-year-olds, Milos Raonic and Grigor Dimitrov, broke through to their first major semifinals at Wimbledon. this year’s U.S. Open will be the tipping point for the rise of a new generation. But recent history suggests that if an outsider seizes on the trace of vulnerability in the “Big 4” to win in New York, it’s more likely to be a veteran. “We didn’t have many young players who were able to challenge for top spots and win Grand Slam titles,” Wimbledon champ Novak Djokovic said. “So this is something that is happening now, but it’s still a long way to the Grand Slam title. It’s not something that can happen overnight.”

It was then-28-year-old Stan Wawrinka who snapped the streak of 16 straight Grand Slam titles by Djokovic, Roger Federer, Rafael Nadal and Andy Murray when he won the Australian Open in January. The only other men in the U.S. Open field who have reached a major final in the past five years are 32-year-old David Ferrer and 28-year-old Tomas Berdych. The player with the most impressive performance leading up to this tournament was a 29-year-old. Jo-Wilfried Tsonga, the runner-up at the 2008 Australian Open, beat Djokovic, Murray, Dimitrov and Federer to win the title at Toronto earlier this month.

As the sport has grown more physical, Grand Slam championships became less likely not only for teenagers but for players in their early 20s.

“Everybody realizes that you’re reaching your peak physically maybe a little bit later and then they’re staying there longer, because they have the technology and they’re more systematic about their training,” said Patrick McEnroe, the U.S. Tennis Association’s general manager of player development.

So a group of men who aren’t that young by tennis standards have gained little experience of playing in the highest-pressure moments. The oft-repeated stat is that the Big 4 have won 36 of the past 38 Grand Slam titles.Contrast that to the five years before Nadal won his first major championship at the 2005 French Open to start that streak. As Pete Sampras’ reign was ending and Federer’s beginning, 12 different players won the 20 Grand Slam titles; for six of them, it would be their only major championship. Now, it’s daunting not just to win championships but to even get close to them.Since Murray reached his first major semifinal at the 2008 U.S. Open, the Big 4 have hogged 63 of the 96 slots in the semis. And since the 2006 French Open, the first Federer-Nadal major final, they’ve filled 58 of the 68 spots in Grand Slam title matches. “It’s definitely been a tough time for everybody else trying to break through,” Raonic said. —AP

Important results: Women’s singles: 14-Lucie Safarova (Czech Republic) bt Timea Babos (Hungary) 6-4, 7-5; 6-Angelique Kerber (Germany) bt Ksenia Pervak (Russia) 6-2, 3-6, 7-5; 2-Simona Halep (Romania) bt Danielle Collins (US) 6-7(2), 6-1, 6-2; 4-Agnieszka Radwanska (Poland) bt Sharon Fichman (Canada) 6-1, 6-0.

Men’s singles: Nick Kyrgios (Australia) bt 21-Mikhail Youzhny (Russia) 7-5, 7-6(4), 2-6, 7-6(1); Matthew Ebden (Australia) bt Tobias Kamke (Germany) 6-4, 6-3, 7-6(2); 23-Leonardo Mayer (Argentina) bt Albert Montanes (Spain) 6-2, 3-0.