President of Baseball Operations David Dombrowski made the announcement.
Bogaerts, 24, earned his first career All-Star Game selection and his second consecutive Louisville Slugger Silver Slugger Award in 2016, recording career highs in games (157), runs (115), home runs (21), RBI (89), walks (58), stolen bases (13), on-base percentage (.356), and slugging percentage (.446). He became the first player in franchise history to win multiple Silver Slugger honors as a shortstop, as well as the first Red Sox ever to hit 20 home runs in a season at the position before turning 24 years old. His 192 hits ranked tied for seventh in the major leagues and led American League shortstops, while his 26-game hitting streak from May 6-June 2 was the third-longest in the majors all season.
Bradley, 26, hit .267 (149-for-558) with an .835 OPS in 2016, recording 30 doubles, seven triples, 26 home runs, 87 RBI, and 94 runs scored in 156 games with Boston. He was one of three finalists for the American League Rawlings Gold Glove Award in center field after leading all major leaguers at the position with 13 assists. Bradley's 29-game hitting streak from April 24-May 25 was tied for the fourth-longest in Red Sox history and helped earn him an AL Player of the Month honor for May. Selected by the Red Sox in the supplemental round of the 2011 June Draft (40th overall), he was chosen to start the 2016 MLB All-Star Game via the fan ballot, his first ever appearance in the midsummer classic.
Holt, 28, batted .255 (74-for-290) with a career-high seven home runs in 2016, appearing in 94 games and missing 37 while on the disabled list. The Red Sox went 46-30 in his starts, which came in left field (55 games), third base (11), second base (4), shortstop (4), and right field (2). The left-handed batter recorded career bests in outfield assists (6) and outfield double plays (2), and for the second consecutive year he was selected as the club's nominee for the Roberto Clemente Award. Holt started each of Boston's three American League Division Series games at third base and led the club with four hits in the series. He went 3-for-4 with a home run in Game 1 of the series, his postseason debut.
Kelly, 28, split the 2016 season between Boston and Triple-A Pawtucket, appearing in 20 games (six starts) over three major league stints. After beginning the season in Boston's starting rotation, Kelly moved to the bullpen and went 2-0 with a 1.02 ERA (2 ER/17.2 IP) in that role. Following his final recall on September 2, the right-hander appeared in 11 games and posted a 0.64 ERA (1 ER/14.0 IP) with 20 strikeouts, three walks, and a .180 opponent batting average (9-for-50). After he allowed zero runs in 12 of his final 13 outings of the regular season, Kelly appeared in each of the Red Sox' ALDS games against Cleveland, retiring all 11 batters faced and recording three strikeouts in 3.2 innings.
Leon, 27, began the 2016 season with Pawtucket before joining the major league club in June and becoming the Red Sox' primary catcher. The switch-hitting backstop played in more games (78) and recorded more hits (78), doubles (17), home runs (7), RBI (35), and runs scored (36) than he did in his first four major league seasons combined. His .310 batting average was the highest by a Red Sox catcher (minimum 250 at-bats) since Carlton Fisk batted .315 in 1977, while he caught three shutouts, posted a 3.90 catcher's ERA, and threw out 13 of 33 (39.4%) attempted base stealers. Leon started each of the Red Sox' ALDS games at catcher and homered in Game 1, his first ever postseason appearance.
Ross, 27, posted a 3.25 ERA (20 ER/55.1 IP) and a career-best 9.11 strikeouts per nine innings in 2016, his second season with the Red Sox. He held left-handed hitters to a .188 batting average (15-for-80) and zero home runs, extending his homerless streak against lefties to 164 batters faced dating back to 2015. Ross retired 42 of 54 first-batters faced and stranded 25 of 34 inherited runners. In his final 31 appearances of the season (beginning July 4), the left-hander went 3-1 with a 1.52 ERA (5 ER/29.2 IP), as 16 of his final 18 appearances were scoreless. He made his postseason debut in Game 2 of the ALDS, when he struck out the only batter he faced.
Thornburg, 28, set career highs for the Milwaukee Brewers in 2016 with 67 appearances, 67.0 innings pitched, eight wins, 13 saves, and 90 strikeouts. Among National League pitchers with at least 50.0 innings pitched, he finished eighth in ERA (2.15), seventh in WHIP (0.94), third in opponent batting average (.162), and fifth in strikeouts per nine innings (12.09). He became Milwaukee's full-time closer on August 1, and in 23 games after that date he went 4-1 with 11 saves and a 1.85 ERA (5 ER/24.1 IP). During a stretch of 49 appearances from May 13-September 22, he posted a 0.54 ERA (3 ER/49.2 IP) and .116 opponent batting average, allowing zero earned runs in 46 of those outings.