In 1999, Martínez was runner-up for the American League (AL) Most Valuable Player Award, after winning the pitching Triple Crown with a 23–4 record, 2.07 ERA, and 313 strikeouts, and—along with Johnson—joined Gaylord Perry in the rare feat of winning the Cy Young Award in both the American and National Leagues (a feat since accomplished by Roger Clemens, Roy Halladay, Max Scherzer, and Blake Snell).

Martínez dominated while pitching most often in a hitter-friendly ballpark and facing some of the toughest competition during the steroid era, which is generally thought to have favored batters.

He then pitched briefly for the Azucareros del Este, before rejoining Licey in 1991–92 in a nine-player transaction that included George Bell, José Offerman and Julio Solano, among others.

"[23] As a minor leaguer in the Dodgers farm system, he was a highly touted prospect although some talent evaluators took issue with his "poise" despite his having a "great fastball and circle-changeup.

Martínez turned in a strong 1993 season as the Dodgers' setup man, going 10–5 with a 2.61 ERA and 119 strikeouts, in 65 games; his 107 innings led all NL relievers.

[26] With the Dodgers in need of a second baseman after a contract dispute with Jody Reed, Martínez was traded to the Montreal Expos for Delino DeShields before the 1994 season.

The 13 complete games were tied for the second-highest single-season total in the modern era of baseball since Martínez's career began (Curt Schilling had 15 in 1998; Chuck Finley and Jack McDowell also reached 13 in a year).

Approaching free agency, Martínez was traded to the Boston Red Sox in November 1997 for Carl Pavano and Tony Armas Jr. Martínez was subsequently signed to a six-year, $75 million contract (with an option for a seventh year at $17 million) by Red Sox general manager Dan Duquette, at the time the largest ever awarded to a pitcher.

Martínez paid immediate dividends in 1998, compiling a 19–7 record and finishing second in the American League in ERA, WHIP, strikeouts, and Cy Young Award voting.

[28] The MVP result was controversial, as Martínez received the most first-place votes of any player (8 of 28), but was omitted from the ballots of two sportswriters, New York's George King and Minneapolis' LaVelle Neal.

[29] Buster Olney, writing for The New York Times, mused that the sentiment that pitchers should not be considered MVP candidates due to the existence of the pitcher-specific Cy Young Award may have cost Martínez the victory.

[29] King later wrote in The New York Post that he left Martínez off of his ballot because he believed that, since they only appear in a fraction of their team's games, starting pitchers should only be considered for the Cy Young Award.

He struck out National League players Barry Larkin, Larry Walker, Sammy Sosa, Mark McGwire, and Jeff Bagwell in two innings pitched, earning All-Star Game MVP for his performance.

[6][39][43] Though he continued his dominance when healthy, carrying a sub-2.00 ERA to the midpoint of the following season, Martínez spent much of 2001 on the disabled list with a rotator cuff injury as the Red Sox slumped to a poor finish.

At the end of May, he was 5–1 with a 2.50 ERA, with 88 strikeouts and 17 walks and 44 hits allowed in 76 innings; Martínez's record was worse than it could have been, with the Mets bullpen costing him two victories.

But his last start was a crucial 3–0 loss to St. Louis in the final week of the 2007 Mets' historic collapse; Martínez provided a good pitching performance (7 IP, 2 ER, 7 H, 1 BB, 8 K) but his teammates failed to score.

Following his return, his fastball typically topped out in the 90–91 mph range,[52] a lower velocity than he'd had during his prime but slightly higher than in recent seasons.

In his return to New York on August 23, Martínez's win against the Mets was preserved by a rare unassisted triple play by second baseman Eric Bruntlett in the bottom of the ninth inning.

At the pre-game press conference, he seemed to relish the attention, telling reporters, "When you have 60,000 people chanting your name, waiting for you to throw the ball, you have to consider yourself someone special, someone that really has a purpose out there.

"[58] Martínez pitched effectively in his second-ever World Series start, but left the game in the 7th inning trailing, 2–1, and wound up taking the loss.

Before his second start of the Series, Martínez called himself and opposing pitcher Andy Pettitte "old goats", and acknowledged that Red Sox fans were rooting for him: "I know that they don't like the Yankees to win, not even in Nintendo games.

[68][69] Reflecting on his career, he named Barry Bonds, Edgar Martínez, Derek Jeter, Kenny Lofton and Ichiro Suzuki as the most difficult hitters he had to face.

On April 13, 1994, in his second start as a Montreal Expo, Martínez lost a perfect game with one out in the eighth inning when he hit Cincinnati's Reggie Sanders with a pitch.

The Davis home run came in the second inning, eliminating any suspense, but sportswriter Thomas Boswell called it the best game ever pitched at Yankee Stadium.

Over the last 3+2⁄3 innings, (11 batters), Martínez threw 53 consecutive pitches without allowing a base runner, and without a single ball being put in play.

Going into the fourth inning, manager Jimy Williams opted to replace Derek Lowe with the ailing Martínez, who had left Game 1 with a back injury.

The Yankees tied the score against Martínez in that inning on four successive hits, leading to a dramatic extra-inning, series-ending victory for New York, costing Grady Little his job with the Red Sox as his contract was not renewed.

In his June 28, 2006 start, Martínez lasted only three innings, and was rocked for eight runs (six earned) on seven hits, losing his worst game as a Met just before going onto the disabled list.

"[95][96] Martínez's four-seam fastball, power curveball, cutter, sinker, and circle changeup were all well above average; combined with his historically excellent control, they proved to be an overpowering package.

Sports Illustrated's Joe Posnanski wrote, "There has never been a pitcher in baseball history—not Walter Johnson, not Lefty Grove, not Sandy Koufax, not Tom Seaver, not Roger Clemens—who was more overwhelming than the young Pedro.