The right-hander struggled a bit during the 2018 regular season, going 4-2 with two saves, a 4.39 ERA, a 1.36 WHIP and 68 strikeouts in 65.2 innings.
It marked a drop-off from his 2017 campaign, when he went 4-1 with a 2.79 ERA, 1.19 WHIP and 52 strikeouts over 58 innings.
Kelly started 73 games over his first four MLB seasons, and he also started six games for the Red Sox in 2016 before Boston decided to exclusively make him a relief pitcher.
He was a key part of the playoff run that yielded a World Series title last season. In 11.1 innings pitched during the postseason, he posted a 0.79 ERA, held batters to a .186 average and registered 13 strikeouts.
The Dodgers were on the receiving end of his dominance during the World Series, and now Kelly figures to become the primary setup man for closer Kenley Jansen in 2019 thanks to his devastating fastball.
Getting to Jansen was an issue at times last season, but with Kelly in the fold, it should allow the likes of Pedro Baez, Josh Fields, Dylan Floro and Tony Cingrani to settle into more suitable roles within the bullpen.