A tantalizing mix of veterans, newcomers, speed and savvy will be on display at the Chevron Houston Marathon and Aramco Houston Half Marathon on Sunday, as top international fields of professional athletes join 25,733 other runners in tackling the streets of the city, cheered by an estimated 250,000 spectators for the city’s largest one-day sporting event.

“This is a year of milestones for us,” said Brant Kotch, race director, in welcoming media to the pre-race press conference on Friday morning. Led by the 25th anniversary of the Run for a Reason Charity Program and the inaugural year of a partnership between Chevron and Aramco in sponsoring Saturday’s We Are Houston 5K, the milestones may also include record-breaking performances and a well-earned birthday party.

In the Chevron Houston Marathon, Ethiopia’s Yitayal Atnafu is seeking to celebrate his 26th birthday by breaking the tape after three consecutive runner-up finishes here. “I am ready to be first this time,” he said Friday. Last year, he led the race by as much as 40 seconds before finishing as runner-up to Bazu Worku, who is not in the field this year.

He will be challenged by, among others, compatriot Abayneh Ayele (the fastest man in the field, with a personal best of 2:06:45); 2017 champion Dominic Ondoro of Kenya; and Albert Korir, a 24-year-old Kenyan who will be racing for the first time in the U.S.

On the women’s side, defending champion Biruktayit Degefa returns for the sixth consecutive year. The Ethiopian’s streak includes victories in 2018 and 2016, a runner-up finish in 2017 and third place in 2015 – the race in which she set her personal best of 2:23:51, the fastest in the women’s field. Her closest rival may be Buze Diriba, a 24-year-old Ethiopian making her debut at the distance. Diriba has seen great success on the U.S. roads, with wins in 2018 at five different distances (5K, 10K, 12K, 10 mile and the half marathon).

For the Americans, 40-year-old Kara Goucher makes her masters debut. The two-time Olympian is running her first marathon since finishing fourth in the 2016 Olympic Marathon Trials, after overcoming a series of injuries. “I’m here for the joy of it,” she said, when asked about her race goals. “I’m here for the love of competing.”

They will all be chasing a first-place prize of $45,000, as well as a race record bonus of $30,000.

In the Aramco Houston Half Marathon, both the men’s and women’s fields are arguably the fastest and deepest ever assembled in this country, with six men bringing personal bests of under 1 hour and six women under 1:07. Few will be shocked if both the men’s and women’s winners run the fastest half marathon ever on U.S. soil: two men come in with personal bests faster than the current mark of 58:46, and four women better or equal the mark of 1:06:29.

Leading the men’s field is Jemal Yimer, a 22-year-old Ethiopian who less than three months ago ran a 58:33 half marathon, tying him for the third-fastest man in history. Not far behind him on the depth chart is Kenya’s Bedan Karoki, the sixth-fastest man in history at 58:42, with another 22-year-old Ethiopian, Shura Kitata (59:16) coming in as one of the best marathoners in the world, having finished as runner-up in 2018 in both London and New York City.

For the women, all eyes will be on Kenya’s Fancy Chemutai, whose personal best of 1:04:52, set in 2018, is only one second off the world record. Sunday will be not only the 23-year-old’s first race in the U.S., but her first in cool temperatures. As of Friday afternoon, the National Weather Service forecast for the 7 a.m. start is for a temperature around 35 degrees and winds of 5-10 mph.

Among her international challengers will be defending champion Ruti Aga of Ethiopia; Kenya’s Mary Wacera (whose winning time here of 1:06:29 is the fastest half marathon ever run on U.S. soil); and Kenyans Gladys Cherono, the 2014 IAAF World Half Marathon Champion and Brigid Kosgei, the 2018 Bank of America Chicago Marathon Champion.

But at least two Americans are also worth watching. Sally Kipyego, the 2012 Olympic silver medalist and 2011 IAAF World Championship silver medalist at 10,000 meters for Kenya, will be running her first race after becoming an American citizen in 2017, and Emily Sisson will be looking to run a personal best that could put her in the record books.

Sisson has twice run the United Airlines NYC Half – in her 2017, she ran 1:08:21 for the fastest-ever U.S. debut – but Houston will her first half marathon on a flat, fast course. The 27-year-old said she is hoping to run under 68 minutes. When asked if she might challenge the American record (67:25) set here last year by her training partner, Molly Huddle, she said, “I know Molly made a comment about her record, and she wouldn’t just say something like that so I’m going to take that as confidence she thinks I’m fit.”

The Aramco Houston Half Marathon athletes will vie for the first-place prize of $20,000, along with a race record bonus of $15,000 and a world record bonus of $50,000.