Coin screamed when Ivanovic's last shot sailed out and then hopped for joy and hit an extra ball high into the stands. Ivanovic quickly gathered her gear and left the court, her hopes of another Grand Slam championship dashed.
"If you would ask if I'm playing like a No. 1, no," Ivanovic said. "Obviously, it was very hard."
Even after Ivanovic struggled in the first round while coming back from an injured thumb, there was no way to see this coming.
Coin spent much of the year playing in minor-league events and recently thought she might give up the sport. Last week, she nearly got knocked out of the qualifying event just to make it into the Open.
It just didn't add up, even to the 25-year-old Frenchwoman with a mathematics degree from Clemson.
Asked whether she'd thought such a win was possible, Coin gave a simple, honest answer.
"No," she said.
And when did she believe it might happen?
"I guess when it was over," she told the crowd at Arthur Ashe Stadium, drawing a huge ovation.
If there was any suspicion that Coin was wavering, she steadied herself by winning 10 straight points in the third set. It was Ivanovic who looked jittery, hitting shots directly into the net or way out.
Never before in the Open era that began in 1968 had the No. 1 woman lost this early in the tournament.
During the first four days at the U.S. Open, almost all of the favorites had won. Handily, too.
But when the Ivanovic-Coin match was moved from the smaller Louis Armstrong Stadium to the main Ashe stage, fans hardly knew what was in store.
Tentative at times, Ivanovic seemed to regain her edge midway through third set. The French Open champ led 40-0 in the fifth game and was about to break Coin's serve when suddenly the momentum shifted.
Coin came back to hold, starting her decisive streak.
Ivanovic tried to stave off Coin in the final game, but it was too late for the 20-year-old Serb star. Coin won on her third match point -- quite a result for someone playing in her first tour-level event.
Coin had tried to qualify for the Australian Open, French Open and Wimbledon and never made any of them. And she certainly wasn't anything bankable going into this match -- she'd earned less than $100,000 lifetime as a pro and was facing someone who'd won nearly $6 million.
Next up for Coin in the third round is No. 32 Amelie Mauresmo, who beat Kaia Kanepi 2-6, 6-4, 6-0. Coin and Mauresmo once played at the same club near Paris and shared the same coach, though don't know each other well.
"I know she was No. 1," Coin said.
Going into this Open, Ivanovic had played only two matches since Wimbledon while her thumb healed. The injury forced her to withdraw from the Olympics before they began, limited her practice time and sent her from Beijing to Australia for treatment.
Pain-free, she made no excuses after escaping against No. 57 Vera Dushevina in the first round.
Four other top players have also been upset in the early rounds -- No. 8 Vera Zvonareva, No. 10 Anna Chakvetadze, No. 13 Agnes Szavay, who lost to Tathiana Garbin 5-7, 6-2, 6-3 and No. 20 Nicole Vaidisova, who lost to Severine Bremond 7-5, 6-3.
The Williams sisters stayed on course for a quarterfinal showdown, with Venus Williams overwhelming Rossana de los Rios in less than an hour and fourth-seeded Serena Williams routing Elena Vesnina 6-1, 6-1 to reach the third round.
No. 6-seeded Dinara Safina, No. 9 Agnieszka Radwanska, No. 17 Alize Cornet, No. 18 Dominika Cibulkova and No. 19 Nadia Petrova also won in straight sets, while No. 30 Ai Sugiyama needed three sets to win.
Venus Williams, champion in 2000 and 2001, did not get much of a workout against de los Rios, 32, who has never gone beyond the second round at Flushing Meadows.
"I think I just had a lot more power than she did today," Williams said.
Williams, 28, said she was satisfied with her performance but she was hardly tested. She made 17 unforced errors and squandered four match points on her serve at 5-3 up before finally claiming victory on the fifth.
Although her sister said this week her second title in 2002 was so long ago she could not even recall holding the trophy, Williams said she had no trouble remembering her last in 2001.
"I won't forget, but I'd like to have a more recent memory, as of like '08. So that's pretty much the goal," said Williams, who won her fifth Wimbledon singles title in July. "I guess, [I'm] kind of overdue, but you've got to win it to deserve it."
Williams has won three of the past four Wimbledon championships but has not reached the final of one of the other Grand Slams since the Australian Open in 2003.
Hovering outside the world's top 10 for three years, Safina must have felt that she was destined to stay in the shadow of her more illustrious brother, Marat Safin.
A recommendation in 2007 from Ivan Ljubicic changed all that.
Ljubicic advised the services of fellow Croat Zeljko Krajan as a coach and since they hooked up, Safina has been almost unstoppable.
"Last year I knew that after U.S. Open I was going to stop [working] with my ex-coach," the Russian world No. 6 said after dispatching Italy's Roberta Vinci 6-4, 6-3 in the second round. "I wanted to work with Heinz Guenthardt but he could not travel a lot. So we needed to find a guy who could.
"I need to thank Ivan Ljubicic because he advised me [about Krajan]. After [the] Australia [Open in January] I decided, OK, I'm going to work with him. First we'll give it a try until French Open. It turned out really good and now we working together. So I think I need to thank Ljubicic or invite him for dinner," grinned Safina, who is one of six players who could top the rankings at the end of the season's final Grand Slam.
Since May, Safina has been the in-form player on the tour and has reached six finals in seven tournaments. That run has included winning titles in Berlin, Los Angeles and Montreal. She also picked up a silver medal at the Olympics. And having contested her first Grand Slam final at Roland Garros, she is eager to go one better in New York.
However, she feels she would never have hit her stride if she was still under the guidance of her former coach, Dutchman Glen Schaap.
"I was working with the Dutch guy for almost two years. At the end we just stopped listening to each other," she said. "He would not accept what I would say. He didn't want to hear my opinions. This is the reason why we started to fight a lot on the court.
"I have enough stress on the court playing a match and if I go for practice and I'm still fighting with my coach, I don't need this. So I decided I better try with somebody else maybe who would listen a little bit more to me," she said.
Her gamble paid off. Asked what Krajan's main contribution has been, Safina, who like her brother has a habit of exploding on court, replied: "I would never imagine that one tennis coach would have so much patience for me."
"I would scream, cry, whatever, and he would say, 'OK, let's go. Keep on going,'" she said.
She has not stopped since.
The 22-year-old Safina has won 17 of her past 18 matches, losing only to Elena Dementieva for the Olympic gold medal. She will next face Switzerland's Timea Bacsinszky, a 6-3, 6-2 winner over Taiwan's Chan Yung-Jan.
Radwanska beat Mariana Duque Marino 6-0, 7-6 (3) and fittingly won the final point at net. Last year, the Polish teen made a splash at the U.S. Open when she startled Maria Sharapova, often walking halfway to the service box and hopping before backing up to receive.
That breakthrough win over Sharapova came in the third round. This time, Radwanska will play Cibulkova in the third round.
Cornet rallied in the first-set tiebreak to fashion a 7-6 (5), 6-1 over Bethanie Mattek. The 18-year-old French teen took advantage of Mattek's four straight misses to close out the opening set.
Mattek is known for her outlandish outfits -- she started out last year's Open in a revealing, metallic gold Wonder Woman get-up and later wore a leopard-print ensemble. Her attire for this match was downright conservative by her standards, featuring a white top that was wide-open in the back and a black skirt.
Now ranked No. 44 after a successful season, Mattek lost in her first matchup with Cornet. Mattek came to the Open without a coach and sometimes uses YouTube to scout players she's never faced.
Cornet stayed aggressive, highlighted by a sequence in the first set when she hit so many overhead slams in succession, the linesman keep retreating to give Mattek more room to maneuver.
In other action,
Information from The Associated Press and Reuters was used in this report.