Mercado was the only American citizen who challenged the boycott of the 1980 Moscow Olympics, competing in boxing for Puerto Rico.
In the professional ranks he had a winning record, but also had some bad luck. He lost to John Montes in a United States title try on points, and on a fight to decide the IBF's #1 challenger, he lost by a knockout in 7 rounds to eventual world champion Antonio Rivera, after leading the fight on all scorecards at the end of round 6.
Mercado now works as a fireman in Dade County, Florida. He is a native of Caguas, Puerto Rico, who used to train at the famous Bairoa Gym, but he resided in Cayey during his years as a top boxing contender.
He had a professional record of 31 wins, 14 losses and 1 draw (tie), with 27 wins by knockout.