The 2002 marked a significant breakthrough for Kosgei in both track and road running. In May, he led the Kenyan team to victory at the 2002 IAAF World Half Marathon Championships with a time of 1:00:39. He edged out Jaouad Gharib to win the race on his first attempt at the half marathon distance. His first time success did not make him an immediate convert, however: "I have changed my focus from the steeplechase to the 10,000 metres ... Maybe in two or three years I will start to think about running the marathon". Kosgei became the Kenyan champion over 10,000 m that summer, and his next test came at the 2002 Commonwealth Games in Manchester, England. He was entered into the 10,000 m race and was second behind his Kenyan compatriot Wilberforce Talel – Kosgei's finishing time of 27:45.46 was seven hundredths of a second behind Talel, who broke the Games record for the event.