The Atlanta Braves' revolving door of relief pitchers continued turning on Friday afternoon with the signing of veteran right-hander Edwin Jackson.

Jackson, 31, replaces struggling rookie reliever Ryan Kelly, who was optioned to Triple-A Gwinnett, on the 25-man roster and is expected to be available for Atlanta's series opener against the Arizona Diamondbacks on Friday night.

A longtime starter in both the American and National Leagues, Jackson transitioned to a relief role with the Chicago Cubs this season, posting a 3.19 ERA in 31 innings pitched. Jackson, who went to high school in nearby Columbus, Ga., was released by Chicago in late July and is still owed the remainder of his four-year, $52 million deal that runs through the 2016 season --€” a debt for which the Cubs are responsible.

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Jackson will be the 28th reliever to pitch for Atlanta this season as injuries (Jason Grilli, Shae Simmons), recent trades (Jim Johnson, Luis Avilan) and suspensions (Arodys Vizcaino, Andrew McKirahan) have opened the door for a variety of candidates. Most of those options have fallen short. The franchise has actively monitored the market for veteran pieces to pick up the slack, adding Jackson, Ross Detwiler, Jason Frasor and others throughout the year.

Overall, the Braves bullpen still ranks among baseball's worst, posting a 4.24 ERA (28th), 3.97 fielding-independent pitching (23rd) and 0.4 wins above replacement (26th) -- only the Texas Rangers have been worse in each of those three categories.

If Jackson can pitch like he did out of Chicago's bullpen this season, he'll at least be a marginal improvement.