Kansas City designated Blanton for assignment Tuesday after trading for the Reds' Johnny Cueto and quickly worked out a deal with Pittsburgh.
Blanton pitched well in a limited role for the Royals, bouncing back from a tough 2013 and a year off in 2014 as he went 2-2 with a 3.89 ERA in 41 2/3 innings over 15 appearances.
He has made four starts this season, recording a 5.30 ERA and allowing 21 hits in 18 2/3 innings. But he's been effective as a reliever, striking out 23 batters and walking only three in 23 innings while logging a 2.