De Los Santos was optioned to Triple-A Lehigh Valley on Sunday, Todd Zolecki of MLB.com reports. De Los Santos struck out four over two scoreless innings Sunday against the Nationals prior to the demotion.
After getting knocked around in his first big-league outing of the season April 27 against Miami (two runs over one inning), De Los Santos looked like a completely different pitcher Sunday. However, in an effort to add a fresh arm prior to Monday's series opener against the Cardinals, De Los Santos will head back down to the minor leagues.