The Pittsburgh Pirates, mired in last place and about to expand their roster to get extended looks at prospects in their organization, released veteran outfielder Gregory Polanco on Saturday.

Pirates manager Derek Shelton, in his availability with reporters before Pittsburgh's game vs. the St. Louis Cardinals, said that informing Polanco of the team's decision "was probably one of the most challenging things I've done."

Polanco, 29, struggled this season but in a franchise that often jettisons its players when contracts become expensive, the right fielder had staying power in Pittsburgh. He broke into the majors in 2014, appearing in 89 games, and he topped 100 games for the Pirates five more seasons including this year, when he hit .208 with 11 home runs and 36 RBIs in 107 contests.

"The thing I respect the most about Gregory Polanco: Every single day -- regardless of what he did at the plate, what his at-bats were -- every day, he had the big smile on his face," Shelton said. "He was a great teammate."

Polanco ends his Pirates career on a bit of a hot streak, which might make him attractive for contending teams down the stretch. He went 6-for-11 in his past four games, and leaves as the team's leader in stolen bases (14).

"Gregory has been a true professional throughout his entire Pirates career, including in our conversation with him regarding today's roster move," general manager Ben Cherington said in a statement. "He has been a great teammate who always handled himself with class and took a great deal of pride in representing the Pirates and the city of Pittsburgh. We wish him nothing but success moving forward."

The Pirates will recall infielder Cole Tucker from Triple-A Indianapolis to fill Polanco's roster spot. This will be Tucker's third stint in Pittsburgh this season. He has appeared at both shortstop and first base with the Pirates.