Martínez represented his nation Puerto Rico at the 2008 Summer Olympics in Beijing, where he competed for the men's 400 metres. He ran in the sixth heat against seven other athletes, including Trinidad and Tobago's Renny Quow and Bahamas' Michael Mathieu. He finished the race in seventh place by sixteen hundredths of a second (0.16) behind Grenada's Joel Phillip, outside his personal best time of 46.46 seconds. Martínez, however, failed to advance into the semi-finals, as he placed forty-fourth overall, and was ranked farther below three mandatory slots for the next round.