As reported by the Pirates' official Twitter account (and relayed by valued commenter "Thunder"), the Bucs have signed right-handed relief pitcher Lisalverto Bonilla to a major league contract, and created a spot for him on the 40-man roster by designating left-handed starter Jeff Locke for assignment.
Bonilla is a Dominican player who began his career as a relatively unheralded signing for the Phillies. He has fairly pedestrian low 90s velocity on his four-seam fastball and an unexceptional breaking ball, but his changeup is a swing-and-miss pitch at its best, allowing him to post good strikeout numbers during his climb through the minors. He was shipped to the Rangers in the Michael Young trade and worked his way onto the Rangers' 25-man roster in 2014, but then injured his elbow. The Rangers placed him on waivers, the Dodgers claimed him and carried him through his 2015 rehab year, and he spent 2016 pitching for Los Angeles's minor league affiliates in AA and AAA, working both in the rotation and out of the bullpen. Between the two levels, Bonilla posted a 3.97 ERA and a 1.34 WHIP in a pair of reasonably difficult offensive environments, with 118 strikeouts in 111 innings pitched. He also experienced a notable increase in his groundball rate, which had been fairly neutral in prior seasons. Most recently, he had been pitching for Escogido in winter ball, though it's difficult to draw any real conclusions from that stint because he appeared in only 5 2/3 innings for that club. Oh, and he's a switch hitter, which is irrelevant, but also kind of nifty.
Bonilla does have some history as a starting pitcher (and the Pirates' Twitter account specifically noted his work as a starter in touting his credentials), so it's possible that the Pirates might allow him to compete for a spot in the rotation this spring, but on the whole, his abilities seem like a better fit for the bullpen. The Pirates enjoyed success with a similar fastball/changeup reliever last year in A.J. Schugel, so perhaps another trip to the same well will be equally beneficial this time. The signing of Bonilla is also interesting in that the team is giving a major league contract to a minor league free agent, mirroring last offseason's signing of Trey Haley. Ideally, this move will turn out better than that one did.
The other half of the coin is the DFA of former All-Star and NL walks leader Locke, who has by turns tantalized and exasperated Pirates fans since his debut in 2011. The decision to designate him for assignment means that the team still has the option of trading him to another club for a nominal return, as they did under similar circumstances with former first baseman Ike Davis, and in this offseason's weak pitching market he may seem like an attractive (or at least palatable) option for someone. While there are things to like about Locke, his results in 2016 were a significant disappointment, and he didn't seem to be on the same page as the coaching staff. He was eligible for arbitration and projected to earn an award of slightly over $4M, and with the team's evident financial constraints, they may have seen that forecast as excessive for what he brings to the table.