Sammy Kitwara of Kenya stands out as Tsegaye Kebede's main contender. As the fifth-fastest man in history over the half marathon distance, Kitwara will toe the line in the Windy City for the fourth time after steadily rising in the ranks over the past three years.

He finished the Chicago Marathon fourth in 2012, third in 2013 and second in 2014. He set a new personal best last year at 2:04:28, making him the fastest man in this year's elite field.