He saw little playing time in the Galaxy, appearing mostly a substitute, before being traded to the Tampa Bay Mutiny in exchange for Jorge Salcedo.

He stayed with the MetroStars from 2000 to 2002, but was a part of a blockbuster trade in the middle of 2002, which sent him along with Brian Kamler and Diego Serna to the New England Revolution for Mamadou Diallo, Andy Williams, and Ted Chronopoulos.

Despite being a starter for the Revolution, Hernández expressed displeasure with his situation, requesting a trade to his home state Dallas Burn.

The Burn, however, were unwilling to make such a trade, and upon the emergence of an adequate replacement for him in Shalrie Joseph, Hernández was transferred to Mexican club Necaxa mid-season 2003.

To the surprise of many, Hernández – called Demetrio in Mexico – earned a starting position as a central defender on the club.