Answer by taking a quote from the following article:

Ryan was born in Refugio, south of Victoria in south Texas, the youngest of six children, to Lynn Nolan Ryan Sr. (1907-1970), and the former Martha Lee Hancock (1913-1990). The senior Ryan operated a newspaper delivery service for the Houston Post that required him to rise in the early morning hours to prepare 1,500 newspapers for delivery over a 55-mile route. The children were expected to help with the daily tasks.

In 1965, after graduating from Alvin High School, Ryan was drafted by the New York Mets in the 12th round of the 1965 Major League Baseball draft. He was assigned the minor league Marion Mets in the Appalachian League. When Ryan was called up to the New York club the following year, he was the second-youngest player in the league. His first strikeout was Pat Jarvis, and he gave up his first major league home run to Joe Torre, a future NL MVP and Hall of Fame big-league manager.  Ryan missed much of the 1967 season due to illness, an arm injury, and service with the Army Reserve; he pitched only 7 innings for the Mets' minor league affiliate in Jacksonville. Ryan returned to the major leagues to stay starting with the 1968 season. Ryan was unable to crack the Mets' pitching rotation, led by Tom Seaver and Jerry Koosman. Ryan was used more as a reliever and spot starter by the 1969 Mets. To deal with frequent blisters on his throwing hand he often soaked his fingers in pickle brine, although the technique's effectiveness was questioned by Ryan's teammates and coaches.  Ryan pitched well for the Miracle Mets in the 1969 postseason. Against the Braves in the NLCS, Ryan completed a Mets sweep by throwing seven innings of relief in Game 3, getting his first playoff win (it would take him 12 years to get another). Then in the 1969 World Series, Ryan saved Game 3, pitching 2 1/3  shutout innings against the Baltimore Orioles. The Game 3 victory gave the Mets a 2-1 lead in the Series, which they went on to win in five games. It would be Ryan's only World Series appearance in his career.  On April 18, 1970, Ryan tied a Mets record by striking out 15 batters in one game. Four days later, Ryan's teammate, Tom Seaver, topped it with a then MLB record 19 against the San Diego Padres (though Ryan would tie this record four years later). Ryan has credited his time with Seaver and the Mets with turning him from just a flamethrower to a pitcher. Contrary to popular belief, Ryan never wanted to be traded from the Mets and felt betrayed by the team that drafted him. His views on this only calmed once he started running the Rangers and gained a better understanding of the business side of baseball.

What did this lead too
When Ryan was called up to the New York club the following year, he was the second-youngest player in the league.