He left with an aching hip and, far worse, an aching heart.
Keflezighi was back Sunday, wiping away tears after the New York City Marathon - for his historic victory for his country, for his recovery from an injury he once feared might end his career.
And for Ryan Shay, his friend who collapsed and died at the U.S. Olympic trials in New York in 2007.
The 34-year-old Keflezighi became the first American man since 1982 to win the NYC Marathon, the latest twist in the story of a family that fled war to thrive in a new home.
"It can't get any better," Keflezighi said.
Derartu Tulu of Ethiopia was the women's winner, capping a stunning comeback of her own on a day when record field of nearly 44,000 started the 40th edition of this race. Two-time defending champion Paula Radcliffe fell back to fourth, hobbled by tendinitis behind her left knee.
Keflezighi won silver at the 2004 Olympics, the first American man to medal since 1976. Sunday's race proved how much depth the U.S. now boasts: With the event doubling as the national championship, six Americans finished in the top 10 for the first time since '79.
Eleven years ago, Keflezighi wrote a letter to Alberto Salazar, the last American man to win in New York. Salazar was working with Nike, and Keflezighi told him that for U.S. distance running to thrive, athletes needed the funding to allow them to train full-time.
That same year, Keflezighi became an American citizen. He was born in Eritrea, growing up in a hut with no electricity. Soldiers would surround his village, looking for boys 12 and older to drag off to war.
When he was 10, his family moved to Italy; two years later, they came to the United States. Keflezighi began running in junior high in San Diego, then went on to star at UCLA.
"Definitely today wearing that USA jersey got the crowd going," he said. "Definitely wore it with big honor and pride."
Tulu's breakthrough victory came 17 years ago at the Barcelona Olympics, when she won the 10,000 meters to become the first black African woman to capture a gold medal. She took gold again in 2000, then won her only previous major marathon title in London the following year.
Tulu had struggled with her weight and endurance after the birth of her second daughter three years ago. But when she ran well at a half-marathon in Philadelphia on Sept. 20, the 37-year-old decided to enter New York.
Asked about the significance of this win, Tulu said she plans to compete at the London Olympics in 2012 when she is 40. "I hope to be able to bring another victory for my country," she said, "so I hope you will be there to ask me the same question."
She needs look no further than Ludmila Petrova for proof she can still succeed at that age. The 41-year-old Russian was the runner-up for the second straight year, as Tulu pulled away in the final mile. Christelle Daunay of France was third.
Tulu won in 2 hours, 28 minutes, 52 seconds, as 14 mph winds slowed the runners on a cool day.
Radcliffe said she felt a twinge behind her left knee two weeks ago as she was completing her training for the marathon. She was hoping the tendinitis wouldn't bother her Sunday but started feeling pain at the 11-mile mark.
She still thought she had a chance when the other runners in the lead pack didn't push the pace, but she couldn't keep up when they finally pulled away in the 22nd mile.
"The really frustrating thing is I don't even feel tired now," she said, "but my legs couldn't go any quicker."
Tulu and Radcliffe have had plenty of duels over the years on the track and in cross country. But Tulu had never been able to keep up very long with the Brit in any marathon.
"I was disappointed to see her falling back and struggling," Tulu said. "I actually tried to encourage her to get her to keep up with us. At some point it was clear that she was not able to do so, and I'm actually disappointed that she was not able to run that well."
Keflezighi pulled away from Robert Cheruiyot of Kenya in the 23rd mile to beat the four-time Boston Marathon champ by 41 seconds. His time of 2:09:15 was a personal best.
Morocco's Jaouad Gharib finished third, and Ryan Hall, who won the trials in New York two years ago, was fourth. Defending champion Marilson Gomes dos Santos of Brazil did not finish.
Keflezighi hobbled to eighth at the trials two years ago, then later found out he had a stress fracture in his hip. Long days of rehab followed, and he didn't feel 100 percent until early this year.
"A lot of people were kind of starting to write him off, saying he's older and he's had too many injuries and all this," said Hall, Keflezighi's neighbor and occasional training partner in Mammoth Lakes, Calif.
Keflezighi made his marathon debut in New York in 2002, finishing ninth. He was second in 2004 and third in 2005. After all that has happened to him in this city, where better to earn his first major marathon victory?
When he ran by the spot where Shay collapsed, Keflezighi crossed himself.
"To get the second chance - you know, unfortunately Ryan is not here," he said. "But injuries are something that you recover from. A lot of things you can recover from in life."