With Mike Trout's injury, the Angels were looking for a suitable replacement. Although Pillar doesn't have the same offensive abilities, he makes up for it with his outstanding defense in Centerfield.
Pillar played for the Braves last season, Despite a modest .228/.248/.416 slash line, Pillar retained his spot with Atlanta throughout the season.
Pillar is struggling this season for the White sox, hitting only .160 in 17 games, but as a depth player and defensive specialist, he can be very useful for the Angels.