A relative late-comer to the sport, he made his first impact in the 2013 season at the age of 23. He won the 800 m at the
Meeting Grand Prix IAAF de Dakar, setting a personal best of 1:45.40 minutes. In his first race in Europe, he went under one minute and 45 seconds for the first time to take fourth at the
Golden Spike Ostrava. He placed a narrow second to
Anthony Chemut at the Kenyan trials in July, improving further to 1:44.38 minutes. This led to his selection for the
2013 World Championships in Athletics. At the competition, he progressed to the semi-final and initially placed fifth but was disqualified for a lane infringement. He ended the year with two performances on the
2013 IAAF Diamond League circuit, coming third at both the
Weltklasse Zürich and the
Memorial Van Damme. The latter race was the fastest in the year, and Rotich's time of 1:43.22 minutes ranked him as the third fastest in the world that season, making it a rapid rise for the athlete who was unranked in 2012. At the first meet of the
2014 IAAF Diamond League in
Doha, he came third. He was chosen for the
4×800 metres relay team (alongside
Sammy Kibet Kirongo,
Job Koech Kinyor and
Alfred Kipketer) at the inaugural
2014 IAAF World Relays event and leading off for Kenya he helped the team to the gold medal. At the
2015 Athletics Kenya World Championship Trials, Rotich shocked world record holder
David Rudisha in the
800 metres, beating him by almost half a second to qualify for the
2015 World Championships in Athletics. ==International competition record==