Velasquez began his second stint on the 15-day injured list because of elbow inflammation May 28.
He was reinstated from the IL on May 27 to make a start at Seattle, but he allowed four runs on seven hits in two innings of a 5-0 loss to the Mariners.
Velasquez, 31, is 4-4 with a 3.86 ERA in eight starts in his first season with Pittsburgh after signing a one-year, $3.15 million deal in December.
He is 38-51 with a 4.88 ERA in 191 career games (144 starts) with five teams since making his MLB debut in 2015.
Also Friday, the Pirates recalled outfielder Canaan Smith-Njigba from Triple-A Indianapolis and designated right-hander Chase De Jong for assignment.
Report – Pirates’ Vince Velasquez has season-ending elbow surgery