Cook, 28, appeared in five games over three stints with Boston last season after being acquired from the Oakland Athletics on July 31. In nine major league outings between Boston and Oakland in 2015, he went 0-2 with 18 earned runs allowed in 8.2 innings (18.69 ERA). An American League All-Star with the A's in 2012, Cook is 13-12 with 17 saves, a 3.43 ERA (79 ER), and 210 strikeouts over 207.0 innings in 217 career major league outings, all in relief, between the Arizona Diamondbacks (2011), A's (2012-15), and Red Sox (2015).
Machi, 33, split the 2015 season between the San Francisco Giants and Red Sox organizations, making a total of 59 relief appearances. Claimed off waivers from the Giants on July 28, he pitched in 26 games for the Red Sox, going 1-0 with four saves, a 5.09 ERA (13 ER/23.0 IP), and 20 strikeouts. In his big league career, Machi is 12-2 with six saves, a 3.47 ERA (71 ER/184.0 IP), and 148 strikeouts in 189 outings, all in relief, for the Giants (2012-15) and Red Sox (2015).
Ogando, 32, pitched in a career-high 64 games last season, his first year with the Red Sox. Signed as a free agent in January, he led team relievers in innings (65.1) and tied for the team lead in appearances and wins out of the bullpen, going 3-1 with a 3.99 ERA (29 ER/65.1 IP) and 53 strikeouts. Over 247 career outings with Texas (2010-14) and Boston (2015), Ogando is 31-17 with four saves, a 3.44 ERA (180 ER/471.1 IP), and 378 strikeouts.
Craig, 31, made 15 starts and appeared in 36 games over two stints with the Red Sox last season, batting .152 (12-for-79) with a double, a homer, and three RBI while seeing time defensively at right field (9 games, 5 starts), left field (7 games, 4 starts), and first base (6 games, 3 starts). The right-handed hitter spent the majority of the season with Pawtucket, where he ranked third in the International League in on-base percentage (.368) while posting a .274 batting average (94-for-343) with 14 doubles, four home runs, 30 RBI, and 49 walks in 93 games. Craig is a lifetime .276 hitter (506-for-1,831) with 107 doubles, three triples, 59 home runs, 296 RBI, and 143 walks in 534 major league games with the St. Louis Cardinals (2010-14) and Red Sox (2014-15).
Leon, 26, returns for a second season in the Red Sox organization. Acquired from the Washington Nationals in March, he set career highs with 41 games and 33 starts over two stints with Boston. He led major league catchers throwing out 50 percent of attempted base stealers (10 of 20) and ranked second in the AL with a 3.47 catcher's ERA (min. 300 innings behind the plate). The switch-hitter batted .184 (21-for-114) with two doubles and three RBI with the Red Sox, and also appeared in 26 games for the PawSox. In 75 career major league games with the Nationals (2012-14) and Red Sox (2015), Leon has hit .187 (39-for-209) with five doubles, a home run, and eight RBI. His career caught stealing rate of 44 percent (15 of 34) leads all active players with at least 500 innings at catcher, while his 3.31 catcher's ERA ranks third among that group.
Buchholz, 31, went 7-7 with a 3.26 ERA (41 ER/113.1 IP) and 107 strikeouts while allowing just 23 walks and six home runs in 18 starts for the Red Sox in 2015. He was placed on the disabled list on July 11 with a right elbow strain and missed the remainder of the season. A two-time AL All-Star, he is 73-51 with a 3.85 ERA (440 ER/1,028.1 IP) and 806 strikeouts in 169 career major league games, including 167 starts, all with the Red Sox. On Tuesday, it was announced that the Red Sox exercised their 2016 contract option for Buchholz.
Uehara, 40, went 2-4 with 25 saves and a 2.23 ERA (10 ER/40.1 IP) for the Red Sox last season but was limited to 43 appearances due to a right wrist fracture suffered on August 7. The 2015 Red Sox Fireman of the Year ranked among the top AL relievers in opponent on-base percentage (2nd, .233), WHIP (4th, 0.92), opponent batting average (6th, .188), saves (11th), strikeout-to-walk ratio (12th, 5.2), and strikeouts per nine innings (13th, 10.5). Over 337 career major league outings (12 starts) in seven seasons between the Baltimore Orioles (2009), Texas Rangers (2011-12), and Red Sox (2013-15), Uehara is 17-19 with 86 saves, a 2.42 ERA (105 ER/390.2 IP), and 459 strikeouts.
Varvaro, 31, made just nine appearances last season due to a right flexor strain that required season-ending elbow surgery. The right-hander went 0-1 with Boston, allowing five runs in 11.0 innings (4.09 ERA). After being claimed off waivers by the Chicago Cubs on May 3, he was returned to Boston later that month and placed on the disabled list because the severity of his medical condition was not known by the Red Sox at the time of his outright assignment. Varvaro underwent successful surgery to remove elbow calcification in his right arm on May 26 and missed the remainder of the season. In parts of six major league seasons with the Seattle Mariners (2010), Atlanta Braves (2011-14), and Boston (2015), he is 7-9 with one save and a 3.23 ERA (66 ER/183.2 IP), recording 150 strikeouts in 166 appearances, all in relief.
Vazquez, 25, missed the 2015 season recovering from Tommy John surgery on his right elbow, which was performed on April 2. He returned to game action as a designated hitter in September and October in the Fall Instructional League. The right-handed batter has appeared in 55 career major league games, all for the Red Sox in 2014, hitting .240 (42-for-175) with nine doubles, a home run, 20 RBI, and 19 walks for Boston. That year, Vazquez threw out 52% of attempted base stealers (15 of 29).
Workman, 27, missed the entire 2015 season on the disabled list and underwent successful Tommy John surgery on June 15. The right-hander has pitched in 39 major league games in his career, including 18 starts, all with the Red Sox from 2013-14. Workman is 7-13 with a 5.11 ERA (73 ER/128.2 IP) and 117 strikeouts in the regular season and also appeared in seven postseason games during the Red Sox' run to the 2013 World Series Championship.
With these transactions, Boston's 40-man roster will be at 38.