Before changing nationality Maina finished seventh at the 2003 World Indoor Championships and fourth at the 2003 World Athletics Final. In 2004 he became Asian Indoor Champion for Bahrain in 3000 metres. This stirred some controversy as he, according to IAAF rules, was not eligible to run for his new country until 16 March 2006. At the end of the season he finished fourth at the World Athletics Final for the second year in a row. However, he was absent from the top international level until late 2006 when he won a silver medal at the Asian Games. Other medalists for Bahrain included Yusuf Saad Kamel, Belal Mansoor Ali and Tareq Mubarak Taher, also imported from Kenya.