Wood attended Belmont High School, where he played in three different sports: baseball, as a pitcher; football, as the starting quarterback; and hockey, as a defenseman.

His father, a semipro baseball player, taught him how to throw a knuckleball while he was in high school, but Wood relied on his fastball and curveball in actual games.

[2][3] Using just two pitches, he helped the baseball team win the state championship in 1959 (his junior year), and he finished his high school career with a 24–2 record.

Wood, however, wanted to play professional baseball, and he was drawing interest from the St. Louis Cardinals, the Milwaukee Braves, and the Boston Red Sox.

He won his only decision in four games with the club, posting a 2.70 earned run average (ERA) before getting promoted to the Raleigh Capitals of the Class B Carolina League.

In his first inning of work, he struck out three San Francisco Giants hitters, prompting the Boston Globe to declare that he would have "spectacular success" in his career.

[4] Sent to the Class B Winston-Salem Red Sox to begin the season, he posted an 8–5 record with a 3.15 ERA, 103 strikeouts, 33 walks, and 99 hits allowed in 111+1⁄3 innings pitched.

He made his major league debut at Fenway Park on June 30, allowing three hits and two runs while striking out three over the final four innings of a 10–2 loss to the Cleveland Indians.

[2] In the second game of a July 19 doubleheader, he made his first major league start (also against Cleveland), allowing three runs in three innings but not getting the decision in an eventual 9–8 defeat.

[9] Promoted to Boston in September, he made one start for the Red Sox on the 22nd, allowing three runs in 7+2⁄3 innings but receiving a no decision in a 4–3 loss to the Washington Senators.

He opened the season with the Class AAA Seattle Rainiers of the Pacific Coast League, but after recording a 1.12 ERA and winning five of seven decisions, he joined the Red Sox in early June.

Boston initially used him as a starter, but he lost four games and allowed 39 hits in 28 innings before getting moved to the bullpen in early July, where he spent the rest of the season.

[2] Spending the next few months in Seattle, Wood posted a 15–8 record, ranking among the league leaders in wins (tied for third with three other pitchers behind Bob Locker's and Ken Rowe's 16), ERA (2.30, second to Bruce Howard's 2.20), strikeouts (197, second to Al Stanek's 220), and innings pitched (211, seventh).

According to Gregory H. Wolf of the Society for American Baseball Research, Wood's "soft-spoken and amiable" nature led to a personality clash with the "brash" Harry Walker, who managed Pittsburgh.

[2] With the Class AAA Columbus Jets of the International League, he had what Wolf called "the hitherto best year of his career at arguably the most crucial point.

"[2] Wood was named the International League's Most Outstanding Pitcher, leading the circuit in ERA (2.41), complete games (15), shutouts (8), and innings pitched (224).

[2][16] Though the Pirates chose not to call him up after the year, his performance impressed George Maltzberger, a scout for the Chicago White Sox, who recommended the pitcher to general manager (GM) Ed Short.

Wood had been reducing it since the previous year, but dispensing with it entirely allowed him to sneakily throw his fastball to hitters, making it a deceptive counterpart to the knuckleball.

[28] On April 13, he had his longest outing of the year, allowing two runs in 5+2⁄3 innings in relief of Gary Peters but earning the win in a 12–7 triumph over the Seattle Pilots.

[28][29] Also against the Pilots in the first game of a June 24 doubleheader, he relieved Dan Osinski with the bases loaded and one out in the sixth inning of a tie ballgame.

[5] On May 26, 1970, Wood relieved Gerry Janeski with one out in the seventh, bases loaded, and the White Sox holding on to a 3–0 lead over Kansas City.

[33] In the second game of a doubleheader against the Oakland Athletics on June 21, Wood struck out four consecutive hitters and five of six he faced in two innings, though the effort came in a 5–4 loss.

[39] Entering the 1971 season, Wood was poised to be a reliever again, but he was added to the starting rotation on the final day of spring training after Joe Horlen broke his leg.

[44] In his final start of the year, against the Brewers on September 29, he allowed one unearned run in a complete game and struck out 10 hitters in a 2–1 victory.

[46] His 189 adjusted ERA+ led the AL, and his Wins Above Replacement (WAR) of 11.5 is the fourth-highest for pitchers since 1920, topped only by Dwight Gooden's 11.9 (1985), Steve Carlton's 11.7 (1972), and Roger Clemens's 11.6 (1997).

"[3] For its June 4 issue, Sports Illustrated had planned to do a cover story on the Indianapolis 500, but rain postponed the race past the editing deadline.

[75] On September 2, he defeated the Royals for his 20th win of the season, pitching 10 innings and retiring Orlando Cepeda on a groundout with the bases loaded to hang on to a 6–4 victory.

[87] His 1976 campaign was cut short on May 9 when a line-drive single hit by Ron LeFlore fractured his left kneecap in the sixth inning of a 4–2 White Sox victory over Detroit at Tiger Stadium.

[95] On September 10, Wood tied a major league record by hitting three consecutive batters in the first inning of a game against the Angels, the latter of which forced in a run with the bases loaded.

[5] After the 1978 season, he became a free agent but attracted "curiously little commotion in the marketplace," which the New York Times News Service speculated might have been due to collusion between the owners.