Martinez, a three-time Cy Young Award winner and eight-time All-Star, spent seven seasons with the Red Sox beginning in 1998 and was a key part of the 2004 team that brought a World Series title to Boston for the first time since 1918.
"I am thrilled to be returning to this organization and to the city I love," Martinez said. "Ben Cherington's meetings this week have been outstanding. It is an honor to be back with the Red Sox and help in any way I can. I am grateful to our leaders; I believe in them, and I thank them for allowing me to return to the field and help us win again. My heart will always live in Boston."
During his 18-year major league career, the native of the Dominican Republic went 219-100 with a 2.93 ERA and 3,154 strikeouts in 2,827.1 innings. His career .687 winning percentage ranks second among modern Major Leaguers (since 1900) behind only Whitey Ford's .690 mark (min. 250 decisions). Among pitchers with at least 2,500 career innings in the majors, only Nolan Ryan (.204) has a lower opponent batting average than Martinez (.214).
With the Red Sox, he went 117-37 with a 2.52 ERA. He has the best winning percentage in franchise history (.760, min. 15 decisions). He also tops club records (min. 1,000 innings) with an average of 11.0 strikeouts per nine innings and a .206 opponent batting average. Among Red Sox all-time leaders, he ranks third in strikeouts (1,683), sixth in wins (117), and seventh in ERA.
In his tenure with Boston, Martinez was the major league leader in winning percentage, ERA, opponent batting average, opponent on-base percentage (.261), opponent slugging percentage (.317), opponent OPS (.578), and WHIP (0.98). He also led all major leaguers in strikeouts per nine innings, the only American Leaguer to average at least a strikeout per inning during that stretch.
He was the starter, winner, and Most Valuable Player of the memorable 1999 All-Star Game at Fenway Park on July 13. He struck out the first four batters he faced: Barry Larkin, Larry Walker, Mark McGwire, and Sammy Sosa. After Matt Williams reached on an error, he then struck out Jeff Bagwell. Williams was then caught stealing to end the inning and the seal the performance.
In his career, Martinez led the Major Leagues in ERA on five occasions, including 1997 with the Expos (1.90) and four times during his first five years as a member of the Red Sox: 1999 (2.07), 2000 (1.74), 2002 (2.26), and 2003 (2.22). He won the AL's strikeout title in 1999 (313), 2000 (284), and 2002 (239).
Martinez finished within the top four in AL Cy Young balloting in each of his six full seasons with the Red Sox (with the exception coming in 2001, when he was limited to 18 starts due to injury).
Martinez was the unanimous winner of the American League's Cy Young Award in consecutive seasons--1999 and 2000. Winning the AL pitching Triple Crown in 1999, he fanned a Red Sox-record 313 batters in 213.1 innings, and set a league record that still stands with an average of 13.2 strikeouts per nine innings. That year, he also set a big league record striking out at least 10 batters in eight consecutive games.
His 1.74 ERA in 2000 is the best single-season mark by an American League pitcher over the last 44 seasons (starting in 1969). In 2000, he established modern major league records for lowest opponent average (.167), lowest opponent on-base percentage (.213), and WHIP (0.74).
Among all Dominican-born pitchers, Martinez has the highest winning percentage, most strikeouts, and ranks second only to Hall of Famer Juan Marichal in both wins and ERA.
Signed originally in 1988 by the Los Angeles Dodgers, for whom he played in 1992 and '93, Martinez also played for the Montreal Expos ('94-'97), the Red Sox ('98-'04), the New York Mets ('05-'08), and the Philadelphia Phillies ('09).
Martinez made a Red Sox-record 11 starts in four seasons of postseason play with Boston and compiled a 3.46 ERA in his 13 outings. He is also the franchise's all-time leader in wins (tied, 6), strikeouts (80), and innings pitched (79.1) in the postseason.
Martinez's last game for the Red Sox was in the 2004 World Series, in which he allowed the Cardinals no runs in seven innings in the club's 4-1 win in Game 3. His last game in the majors was also in the World Series, in 2009, as Philadelphia lost to the New York Yankees.