(Reuters) - Kenyans Geoffrey Kirui and Edna Kiplagat could face serious American challenges when they defend their Boston Marathon titles on Monday.
U.S. Olympic bronze medalist Galen Rupp lost to Kirui by 21 seconds in the 2017 race and is back while New York City Marathon champion - and home state favorite - Shalane Flanagan headlines a group of four top U.S. women's contenders.
Rain and temperatures in the 50s (13 C) after an icy weekend are forecast, making for a messy race day.
That could be a factor, especially for the African athletes.
No American man has won in Boston since 1983, and Kirui, former champions Lelisa Desisa and Lemi Berhanu of Ethiopia, Ethiopian Tamirat Tola, the fastest in the field at 2:04.06, and Kenyan dark horse Nobert Kigen are aiming to keep it that way.
Yet many believe Chicago Marathon winner Rupp will have a say.
"Galen will definitely be much harder to beat than last year, regardless of how the race plays out," Alberto Salazar, his coach and a former Boston champion, told reporters.
"But Kirui or the others may also be in better shape than last year, so it's impossible to predict."
The final few miles proved costly in 2017 to Rupp, who admitted afterwards: "I just did not have it over those last three or four miles."
Kirui, 25, backed up his Boston win, his first victory in a marathon, by taking the 2017 world championship title. He carries a personal best of 2:06:27 to Rupp's 2:09:20.
The U.S. women's drought at Boston stretches back to 1985.
Flanagan, Jordan Hasay, Molly Huddle and Desi Linden will try to change that against an international field that may not be as strong as in past years.
Flanagan, 36, who grew up in Massachusetts, is the sentimental favorite, with Hasay holding the best Boston finish.
The 26-year-old made it to the podium in 2017, finishing third at both Boston and Chicago. The Boston race was her marathon debut.
Linden and Huddle are both experienced marathoners with Linden fourth in Boston in 2017 and Huddle third in the 2016 New York City Marathon.
Kiplagat, the Kenyan mother of five who is now 38, returns to defend her title after finishing second in the world championships and fourth in New York City in 2017.
Aselefech Mergia, a former London winner, and fellow Ethiopian Mamitu Daska, who was third in New York last year, could be Kiplagat's biggest international challengers along with former Boston winners Buzunesh Deba (Ethiopia) and Caroline Rotich (Kenya).
(Reporting by Gene Cherry in Raleigh, North Carolina; Editing by Toby Davis)