Polanco hit .273 (6-for-22) with two doubles and one home run this spring. Last season, he batted a combined .285 with 12 homers and 38 stolen bases in 127 games with Indianapolis, Double-A Altoona and Class A Bradenton.
Welker struggled throughout the exhibition season, giving up six runs and seven hits in 5 1-3 innings for a 10.13 ERA. He walked five and struck out four. He made his major league debut last season with a pair of relief appearances.
The Pirates have 51 players remaining in camp.