Andrew Chafin
The Pirates have very little lefty pitching depth in their bullpen. Joey Wentz currently projects to be their only lefty bullpen arm. Luckily, one of the more underrated lefty relievers in the game recently became a free agent in Andrew Chafin. Chafin's season had some mixed numbers, but he has consistently been a decent reliever throughout his career.
Chafin opened the season with the Detroit Tigers, where he had a strong 3.16 ERA, 2.54 FIP, and 1.38 WHIP in his first 37 innings. Chafin's walk rate was just a hair under 10% at 9.9%, but he struck out a whopping 30.9% of opponents. He was also great at limiting homers, posting an 0.49 HR/9 and 6.3% barrel rate.
Chafin was then shipped to the Texas Rangers at the trade deadline, but his numbers took a sharp decline, as he put up a 4.19 ERA, 5.44 FIP, and 1.66 WHIP in 19.1 innings. Chafin's peripherals also looked much worse. His K% was 23.8%, while his walk rate clocked in at a horrendous 17.9%. Chafin became very home run prone with a 1.40 HR/9 rate. His only silver lining was his barrel rate, which remained constant at 6.1%.
Chafin will be in his age-35 campaign next season. The long-time Arizona Diamondbacks southpaw still recorded a dozen holds this past season, and is no stranger to working in higher leverage. Chafin should be affordable and is definitely someone who would improve the Pirates' bullpen, especially given he is a lefty, something the Pirates do not possess.