Haile Gebrselassie lost the race against time on Sunday when Patrick Makau shattered his marathon world record and ended an era of two decades dominated by arguably the greatest distance runner in history.
His lungs seizing up and struggling for air after more than 17 miles of the Berlin Marathon, Gebrselassie finally quit shortly after mile 21.
By then, Makau was more than two minutes ahead _ on his own and on the way to the German capital's landmark Brandenburg Gate and a new world record.
"I was hoping to gain a lot of experience but not to win," Makau said after slashing 21 seconds from Gebrselassie's old mark.
Makau pulled away after 16 miles and finished in 2 hours, 3 minutes, 38 seconds.
Gebrselassie, whose previous record stood at 2:03.59, pulled up after Makau's breakaway and seemed on the verge of giving up when he stopped running and bent over, holding his chest. After about a minute, he resumed the race.
"He was still feeling good at 25K but then his lungs started tightening up, he could not breathe, we don't know why," Gebrselassie's agent Jos Hermens told The Associated Press.
Gebrselassie suffers from asthma and is allowed to take medicine to treat the condition, but hadn't taken any because he had not had any problems for months, Hermens said.
"Maybe this was a mistake, but he felt fine before, his preparation was good," Hermens said.
Gebrselassie had won four successive Berlin marathons from 2006 and set his world record in 2008.
"This is not the end of Haile, but this is the end of an era," Hermans said.
Makau, whose previous personal best was 2:04.48, also won last year's event in driving rain. Sunday's race on Berlin's flat course took place in sunny, mild conditions.
The 26-year-old Makau brandished a Kenyan flag after coming through the Brandenburg Gate and crossing the finish line.
"Today maybe a new generation is starting in marathon," Makau said. "My body was not good in the morning but I had no problems in the race, I did everything well."
By the 21st mile, Makau was alone in front. "I knew then that I could win the race and break the record," he said.
He and Gebrselassie had stayed together until the 16th mile and were easily on world record pace from the start.
Gebrselassie, 38, pulled out of the New York City Marathon in November with a knee injury and retired immediately after the race. But he changed his mind eight days later.
He injured both knees when he fell during a training run in the rugged countryside of his homeland but came back to win a half-marathon in April in Vienna, Austria. He also won the 10,000-meter Great Manchester Run in May.
Gebrselassie's main objective in Berlin was to run a good time and qualify for Ethiopia's Olympic team.
Hermens said Gebrselassie is not planning to retire again, but that he might have problems qualifying for next year's London Olympics.
"No, no, he is in a much better mood now than in New York, he did not suffer a lot. But qualifying may be a problem now, we don't really know where to get it," Hermens said.
Hermens said Gebrselassie would now probably run in Dubai in January and seek a time of about 2:05 and then have a long rest before London.
"He is not getting any younger, his main goal is go to his fifth Olympics because no long distance runner has done that.
"But the reality is that someone 25 will run faster than someone 38," Hermens said. "We are going to see low 2:03s and high 2:02s soon."
Gebrselassie won Olympic gold medals in the 10,000 meters in 1996 and 2000 and competed in 2004 and 2008 in the distance. He also had four world titles in the 10,000 between 1993 and 1999.
Stephen Kwelio Chemplany, a pacemaker from Kenya, finished second in 2:07.55, and another Kenyan, Edwin Kimaiyo, was third in 2:09.50.
Florence Kiplagat of Kenya won the women's race in 2:19.44 to complete her first marathon, ahead of Irina Mikitenko of Germany and world record holder Paula Radcliffe of Britain, who was making her Berlin debut and competing for the first time since finishing fourth in New York in 2009.
Mikitenko clocked 2:22.18 and Radcliffe finished in 2.23.46.