The move was announced after tonight's game at Chase Field; the return is yet to be announced, but appears to be a minor-league player of some kind. Perez was signed by the Diamondbacks for the 2014 season, and has received a total of $4.25 million for his services last year and this. Overall, Oliver has performed very solidly out of the bullpen, in an area where the team had struggled. Over 116 appearances and 87.2 innings for Arizona he had a 2.98 ERA (129 ERA+), the latter figure ranks fourth in team history, among left-handed relievers with at least 50 innings for the team.
He would have been a free-agent at the end of the season, so this trade is perhaps not too surprising, in terms of getting something for him. The success of Andrew Chafin as a leftie out of the bullpen - he's second on that list mentioned above - may have helped the team decide Perez could be moved. It does appear some of the players may not be quite as convinced:
Hellickson's reaction to Perez being traded: "But...we need him." #Dbacks— Derek Montilla (@Cap_Kaveman) August 8, 2015
OFFICIAL: #Dbacks acquire left-handed pitcher Junior Garcia from the Astros for left-handed pitcher Oliver Pérez.— Arizona Diamondbacks (@Dbacks) August 8, 2015
Garcia certainly lives up to the "Junior" part of his name, being just 19 years old. He was in Low-A ball with Tri-City for Houston, having just been promoted from rookie ball at the end of July. He had made a total of nine appearances this year, six as a starter, with an ERA of just 0.96 and a K:BB ratio of 26:7 in 37.1 innings of work.