Rivas had his contract selected from Triple-A El Paso by the Padres on Friday.
Rivas will join the Padres in San Diego ahead of their four-game series with his former team, the Chicago Cubs. The 26-year-old has produced a .319 average with eight homers, 33 RBI, 40 runs and four stolen bases over 163 at-bats with El Paso this season. In a corresponding move, Jose Azocar was sent down to Triple-A on Friday.