The addition of Manuel, a reliever, put the Red Sox's roster at 32, with the likelihood that there would be no other tweaks before the midnight ET deadline.
The 26-year-old Manuel split last season between the Reds' and Mariners' organizations.
While pitching for Cincinnati's Triple-A Louisville affiliate, Manuel went 3-4 with 10 saves and a 2.70 ERA. After being dealt to the Mariners on July 29, he finished the season at Triple-A Tacoma, going 1-1 with four saves and a 3.32 ERA. In all, he held Triple-A hitters to a .207 average.
Manuel had a cup of coffee with the Reds, pitching 4 1/3 innings of scoreless relief over three appearances.
Aside from Manuel, the Red Sox were comfortable with the players they had protected, and therefore needed no other maneuvering.
As general manager Theo Epstein pointed out on Thursday, the only adjustment that would have been needed was the addition of left-hander Dustin Richardson, but he was placed on the 40-man roster late in the season when the Sox were short on pitching.
Players who signed when they were 19 or older (e.g. college draftees) four years ago, or players who signed at 18 and younger (international signees or high school draftees) five years ago, are all eligible for the Rule 5 Draft if they're not placed on 40-man rosters.
For example, any unprotected college draftees from the 2006 Draft or high school Draft picks from the Class of 2005 are up for grabs.
The most noteworthy player not protected by the Red Sox was left-hander Kris Johnson, who was once highly regarded enough by the club to be the 40th player selected in the 2006 First-Year Player Draft.
Johnson had a decent 2008, going 8-9 with a 3.63 ERA in 27 starts for Double-A Portland. But he took a big step back in '09, going 3-13 with a 6.35 ERA in 22 starts for Triple-A Pawtucket, and 0-3 with a 6.35 ERA in three starts for Portland. Lack of command is a big shortcoming for the 25-year-old Johnson at this stage of the game, but perhaps another team -- for the price of $50,000 -- will take a crack at him. The Red Sox, if they wish, could also add a Rule 5 Draft pick at that same acquisition cost.
The organization's most highly-regarded prospects are either already on the 40-man roster or don't yet need to be because of a lack of service time with the organization.
Pitchers: Daniel Bard, Josh Beckett, Michael Bowden, Clay Buchholz, Manny Delcarmen, Felix Doubront, Jon Lester, Manuel, Daisuke Matsuzaka, Hideki Okajima, Jonathan Papelbon, Ramon Ramirez, Dustin Richardson, Junichi Tazawa and Tim Wakefield.
Catchers: Dusty Brown, Victor Martinez, Jason Varitek and Mark Wagner.
Infielders: Aaron Bates, Jose Iglesias, Casey Kotchman, Mike Lowell, Jed Lowrie, Dustin Pedroia and Kevin Youkilis.
Outfielder: Brian Anderson, J.D. Drew, Jacoby Ellsbury, Jeremy Hermida and Josh Reddick.
Designated hitter: David Ortiz.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.