In return, the Padres acquired four Red Sox' prospects: outfielder Manuel Margot, shortstop Javier Guerra, infielder Carlos Asuaje, and left-hander Logan Allen.
Kimbrel is quite an add for the Red Sox bullpen. The group struggled last season, posting the fifth-highest ERA in the big leagues, as well as a -1.4 Wins Above Replacement, according to FanGraphs, coming in at the bottom of baseball.
Kimbrel is the elite closer and bullpen arm that the Red Sox lacked in 2015.
With Koji Uehara going down to injury late in the year, Boston could never really find any back-end relief pitching to close out games. Kimbrel will probably fill in at closer, with Uehara probably becoming a set-up guy.
Red Sox' president of baseball operations Dave Dombrowski is notorious for not being able to build good bullpens. When Dombrowski was the GM of the Detroit Tigers, their relief pitching would almost always be their downfall. It appears, through this trade, that Dombrowski is prioritizing bullpen with Boston.
Kimbrel is a good asset not only because of his performance on the field, but also because of his payroll obligations.
He is under contract for the next two seasons for just $24 million, with a club option for the 2018 season valued at $13 million with a $1 million buyout. A player of his caliber would definitely be worth more than $12 million per season, which makes him such a valuable addition to the Red Sox.
Last season, Kimbrel was not as good as he had been in the past, but was still plenty good.
The 27-year-old Kimbrel went 4-2 with a 2.58 ERA in 61 appearances out of the Padres bullpen, saving 39 games in 43 opportunities. He posted an 87 to 22 strikeout-to-walk ratio. Even with a solid season, 2015 was the first time Kimbrel had not been voted an All-Star since his rookie season in 2010.
From 2010 to 2014, Kimbrel was by far the best closer in baseball. He led the National League in saves every single season, being named to the All-Star Game in each. Kimbrel was so good that he averaged 46 saves per year during that stretch.
The Braves, Kimbrel's former team, dealt him to the Padres along with Melvin Upton Jr. just before the start of last season, getting four players and a competitive balance draft. With this trade, Kimbrel will be on his third team in as many seasons.
The Padres received what is considered to be a great return for Kimbrel to replenish their prospect system.
All four of the prospects San Diego received for the relief pitcher are amongst the Red Sox' Top 30, according to MLB Pipeline, with Margot checking in at No. 3, Guerra at No. 6, Asuaje at No. 23, and Allen at No. 25.
Margot and Guerra are also included in MLB Pipeline's Top 100 overall prospects, at Nos. 25 and 76, respectively. Margot ended the 2015 season in Double-A; Guerra ended the year in Class-A.