Along with adding Medina and John Jaso (signed to a two-year deal) and losing LaFromboise, the Pirates outrighted reliever Jorge Rondon to Triple-A Indianapolis on Wednesday to keep their 40-man roster full.
Medina, 27, split last year between the Mariners, Cubs and Triple-A, posting a 4.71 ERA in 17 appearances in the Majors. It was a step backward for Medina, who thrived in his first two big league seasons with the Mariners, recording a 2.81 ERA with 131 strikeouts in 125 innings over 129 outings.
"We claimed a reliever that was very effective at the Major League level in 2013-14 that had a bit of a down year in 2015," Pirates general manager Neal Huntington said. "We're going to take the opportunity to see if there are some things we can help him with, a change of scenery and see if we can get him as effective as he was in 2013-14."
Medina has occasionally struggled with his control, walking 4.9 batters per nine innings in the Majors. But he's averaged a strikeout per inning, and his fastball has touched 97 mph.
The Pirates have helped out relievers with similar profiles in the past, most recently picking up flame-throwing righty Arquimedes Caminero from the Marlins and helping him put together a solid season in 2015.
Medina is out of Minor League options, so the Pirates would risk losing him if they don't put him on the Opening Day roster. If he makes the club, Medina will join Caminero in a deep Pirates bullpen that currently features closer Mark Melancon, Watson and right-handers Jared Hughes and Juan Nicasio, another hard-throwing righty the Bucs signed during the Winter Meetings.
Still missing from that relief corps is another left-handed reliever. Aside from Watson, who will set up for Melancon or close if Melancon is traded, the Pirates' only other lefty options are Kyle Lobstein, who is more likely to serve as Triple-A rotation depth, and non-roster invitee Robert Zarate.
The Pirates' need for a lefty reliever to replace Antonio Bastardo was made more obvious Wednesday as they lost LaFromboise to the Angels. Huntington said the Bucs are engaged in dialogue with several potential options.
"We would like to add a quality left-handed pitcher to the staff," Huntington said. "It still has to be quality, and it still has to be someone we believe can come in here and help us be a better bullpen. ... We'll see where that all takes us."