Marichal's delivery was renowned for one of the fullest windups in modern baseball, with a high kick of his left leg that went nearly vertical (even more so than Warren Spahn's delivery).
Marichal maintained this delivery his entire career, and photographs taken near his retirement show the vertical kick only diminished.
The windup was the key to his delivery in that he was consistently able to conceal the type of pitch until it was on its way.

Marichal was discovered by Ramfis Trujillo, the son of late Dominican dictator Rafael Leónidas Trujillo.
Ramfis was the primary sponsor of the Dominican Air Force Baseball Team (Aviación Dominicana), against which Marichal pitched a 2–1 victory game in his native Monte Cristi.
From the very moment the game ended, Marichal was a member of Aviación Dominicana team, enlisted to the Air Force right on the spot by Ramfis's orders.

Marichal entered the major leagues on July 19, 1960 with the San Francisco Giants as the second native pitcher to come from the Dominican Republic.
He made an immediate impression: in his debut, on July 19, 1960 against the Philadelphia Phillies, he took a no hitter into the eighth inning only to surrender a two-out single to Clay Dalrymple.
He ended up with a one-hit shutout, walking one and striking out 12.
He started 10 more games that season, finishing at 6–2 with a 2.66 ERA.
He improved his victory totals to 13 and 18 over the following two seasons, respectively, before finally cracking the 20-victory plateau in 1963, when he went 25–8 with 248 strikeouts and a 2.41 ERA.
He appeared in every All-Star game of the 1960s beginning in 1962.
 In May 1966, he was named NL Player of the Month with a 6–0 record, a 0.97 ERA, and 42 SO.
On July 14, 1967, he surrendered the 500th Home Run of Eddie Mathews' career.

Marichal enjoyed similar success through the 1969 season, posting more than 20 victories in every season except 1967, and never posting an ERA higher than 2.76.
He led the league in victories in 1963 and 1968 when he won 26 games.
In 1968, he also finished in the highest rank of his career in MVP voting, finishing fifth behind Bob Gibson, Pete Rose, Willie McCovey, and Curt Flood.
 He and Sandy Koufax were the only two Major League pitchers in the post-war era (1946–present) to have more than one season of 25 or more wins; both pitchers had three such seasons in their careers.

Marichal won more games during the decade of the 1960s (191) than any other major league pitcher, but did not receive any votes for the Cy Young Award until 1970, when baseball writers started voting for the top three pitchers in each league rather than one per league (or, until 1967, only the top pitcher in MLB).
Marichal finished in the top 10 in ERA seven consecutive years, starting in 1963 and culminating in 1969, in which year he led the league.
During his career, he also finished in the top 10 in strikeouts six times, top 10 in innings pitched eight times (leading the league twice), and top 10 in complete games 10 times, with a career total of 244.
He led the league twice in shutouts, throwing 10 of them in 1965.

Marichal exhibited exceptional control.
He had 2,303 strikeouts with only 709 walks, a strikeout-to-walk ratio of 3.25 to 1.
This ranks among the top 20 pitchers of all time, ahead of such notables as Bob Gibson, Nolan Ryan, Steve Carlton, Sandy Koufax, Don Drysdale, Walter Johnson and Roger Clemens, who each have strikeout-to-walk ratios of less than 3:1.
Over his career, he led the league in the fewest walks per nine innings four times, and finished second three times – totaling eleven years in which he finished in the top 10, all while also finishing in the top 10 for strikeouts six years.
Marichal's delivery was renowned for one of the fullest windups in modern baseball, with a high kick of his left leg that went nearly vertical (even more so than Warren Spahn's delivery). Marichal maintained this delivery his entire career, and photographs taken near his retirement show the vertical kick only diminished. The windup was the key to his delivery in that he was consistently able to conceal the type of pitch until it was on its way.
Marichal was discovered by Ramfis Trujillo, the son of late Dominican dictator Rafael Leónidas Trujillo. Ramfis was the primary sponsor of the Dominican Air Force Baseball Team (Aviación Dominicana), against which Marichal pitched a 2–1 victory game in his native Monte Cristi. From the very moment the game ended, Marichal was a member of Aviación Dominicana team, enlisted to the Air Force right on the spot by Ramfis's orders.
Marichal entered the major leagues on July 19, 1960 with the San Francisco Giants as the second native pitcher to come from the Dominican Republic. He made an immediate impression: in his debut, on July 19, 1960 against the Philadelphia Phillies, he took a no hitter into the eighth inning only to surrender a two-out single to Clay Dalrymple. He ended up with a one-hit shutout, walking one and striking out 12. He started 10 more games that season, finishing at 6–2 with a 2.66 ERA. He improved his victory totals to 13 and 18 over the following two seasons, respectively, before finally cracking the 20-victory plateau in 1963, when he went 25–8 with 248 strikeouts and a 2.41 ERA. He appeared in every All-Star game of the 1960s beginning in 1962.  In May 1966, he was named NL Player of the Month with a 6–0 record, a 0.97 ERA, and 42 SO. On July 14, 1967, he surrendered the 500th Home Run of Eddie Mathews' career.
Marichal enjoyed similar success through the 1969 season, posting more than 20 victories in every season except 1967, and never posting an ERA higher than 2.76. He led the league in victories in 1963 and 1968 when he won 26 games. In 1968, he also finished in the highest rank of his career in MVP voting, finishing fifth behind Bob Gibson, Pete Rose, Willie McCovey, and Curt Flood.  He and Sandy Koufax were the only two Major League pitchers in the post-war era (1946–present) to have more than one season of 25 or more wins; both pitchers had three such seasons in their careers.
Marichal won more games during the decade of the 1960s (191) than any other major league pitcher, but did not receive any votes for the Cy Young Award until 1970, when baseball writers started voting for the top three pitchers in each league rather than one per league (or, until 1967, only the top pitcher in MLB). Marichal finished in the top 10 in ERA seven consecutive years, starting in 1963 and culminating in 1969, in which year he led the league. During his career, he also finished in the top 10 in strikeouts six times, top 10 in innings pitched eight times (leading the league twice), and top 10 in complete games 10 times, with a career total of 244. He led the league twice in shutouts, throwing 10 of them in 1965.
Marichal exhibited exceptional control. He had 2,303 strikeouts with only 709 walks, a strikeout-to-walk ratio of 3.25 to 1. This ranks among the top 20 pitchers of all time, ahead of such notables as Bob Gibson, Nolan Ryan, Steve Carlton, Sandy Koufax, Don Drysdale, Walter Johnson and Roger Clemens, who each have strikeout-to-walk ratios of less than 3:1. Over his career, he led the league in the fewest walks per nine innings four times, and finished second three times – totaling eleven years in which he finished in the top 10, all while also finishing in the top 10 for strikeouts six years.
Juan Marichal