The Pirates optioned De Los Santos to Triple-A Indianapolis on Tuesday, Kevin Gorman of TribLive.com reports.
De Los Santos has been walking a tightrope this season with 13 walks in 24.1 innings out of the Pittsburgh bullpen, but he's been able to work around those free passes for the most part en route to a 3.33 ERA. He'll head down for the time being as the club adds reinforcements, but De Los Santos figures to be back before the end of the season.