Preller said late Wednesday that the team has been watching Pirela for some time, and that the two teams had previously had discussions about him.
Preller credited the work of two of San Diego's professional scouts, Steve Lyons and Tyler Tufts, for staying on Pirela during the season.
While Pirela's versatility probably plays better for a National League team than it does for an American League team, it was his bat that stood out to the Padres.