In the minors he had the distinction of leading the league in some bad categories which slowed his process of getting called up. He led the league in walks (twice), losses and wild pitches thrown. Hamilton would take his control issues with him to the major leagues, as he made his debut with the Philadelphia Phillies in 1962.
He led the league in walks (107) & wild pitches (22) that season, going 9-12 giving up 18 HRs while posting a 5.09 ERA. The next year after going 4-8 at AAA Arkansas he was brought back up to the Phillies staff. He posted a 5.40 ERA & was traded to the Detroit Tigers along with Don Demeter, for Jim Bunning & Gus Triandos.
Over the next two seasons he only pitched in nine games at the major league level, posting an ERA over ten. In May of 1965 he allowed four earned runs in 2/3 of an inning against the Baltimore Orioles & later that month allowed three earned over two innings at Cleveland against the Indians.
Although in the minor leagues that year with AAA Syracuse, he was one of the league's top pitchers, going 12-10 while leading the International league in ERA (.242) .
In October of 1965 the New York Mets purchased his contract.
Hamilton was pretty much described as a jovial guy, who was welcomed in the New York club house. During his pitching days he had also admitted to throwing a spitball.
He pitched the third game of the Mets 1966 season, throwing a complete game victory in his Mets debut. It was a one run, five hitter against the Atlanta Braves in front of 23,000 at Shea Stadium. Jack won three of his first four decisions & that was big deal for the '66 Mets staff.
His third victory was a May 5th classic, a one hitter against a powerful St. Louis Cardinals team in St. Louis. The only hit that day came in the third inning, from future Met & that days opposing pitcher; Ray Sadecki. It was the second one hitter in Mets history.
From there he had a few rough outings, allowing more than three earned runs five times in nine starts. Eventually Hamilton was used as a reliever and became the Mets closer, although there was no such term in those days.
He saved 13 games, which was seventh best in the league, finishing the 1966 season 6-13 with a 3.93 ERA & 93 strikeouts in 148 innings pitched. His wildness continued, throwing 18 wild pitches (second most in the league) & allowing 88 walks.
In 1967 he began the year in the bullpen, but got one start, coming against the St. Louis Cardinals at Shea Stadium on May 20th.
Trivia: Hamilton had his biggest thrill when he hit a grand slam HR off former original Met, Al Jackson that day. The HR came in the 2nd inning with Tommy Davis, Ken Boyer & Jerry Grote all on base. But the Mets eventually went on to lose the game 11-9 with Hamilton getting no decision.
Hamilton is one of only two Mets pitchers to have ever hit a grand slam, Carlton Willey being the other.
Hamilton was 2-0 with a save after 17 games for the Mets before they traded him to the Los Angeles Angels for Nick Willhite who would pitch in four games (0-1) before being done with baseball.
On August 18th 1967 during the tight AL pennant race, the Angels faced the Boston Red Sox at Fenway Park, with Hamilton on the mound. The young Boston star Tony Conigliaro, came to bat, when a Hamilton fastball accidentally hit him in the face. The pitch fractured his eye socket & left cheekbone, leaving him motionless on the ground.
It was one of the worst beanings of all time, as Tony C. almost died in the hospital. He missed the rest of the season and the entire next season. He suffered vision problems that haunted him for the rest of his life. Although he came back in 1969 he was never the same player.
Hamilton did know the severity of the incident at first so he did not rush to see Conigliaro in the hospital. "When I found out how serious it was, I tried to visit him at the hospital but they were only letting the family in," Hamilton told the AP. "I never had a chance to see him or say anything to him after that."
Quotes: Hamilton said in 1987 "It was a high fastball. He didn't move at all. He didn't even flinch, jerk his head or anything. It was hard to sit there and take a pitch like that." In 1992 he said- "I know what I did wasn't intentional. But people are going to remember it, that's just the way it's always going to be. So you have to go on with life."
As for Hamilton, he was never the same player again either. He became afraid to throw inside at hitters for fear of hurting them as well. He was already known for his not having good control & this event totally ruined him.
His strikeouts declined, batters hit him like crazy, and he went 3-11 over the next two seasons before calling it quits in 1969.
In his eight year career he was 32-40 with 357 strike outs 348 walks, 74 wild pitches (218th all time) a 4.53 ERA in 611 innings over 218 appearances. At the plate he hit two HRs with 7 RBIs batting .107.
Retirement: After baseball Hamilton and his wife ran a number of restaurants. He last owned a restaurant called "Jacks Plaza Veiw Restaurant" in the music tourist vacation town of Branson, Missouri.
On February 23rd 2018, Hamilton passed away at the Shepard Hills Living Center in Branson, Missouri at the age of 79.