Phillips spent most of his career in the shadow of his idol, Edwin Moses, frequently as runner up during Moses' unequaled winning streak. He managed to beat him once, at the 1988 Olympic Games in Seoul. In 1983, Phillips finished fifth in the 400 m hurdles at the inaugural World Athletics Championships. In 1985, in absence of Moses, Phillips won his only US National Championship title, and also won the IAAF World Cup. In 1988, Phillips lost to Moses at the Olympic trials, but showed a good pace at Olympics, winning his heat and semifinal. In the final, Phillips ran his personal best 47.19 to win a gold medal, beating second-place Amadou Dia Ba from Senegal by 0.04 seconds. The two times currently still rank them as the #5 and #6 performers of all time. Although Moses ran his fastest Olympic final, he finished only third in a time of 47.56.