In 13 major-league seasons, he appeared in 744 games, 733 as a relief pitcher and 11 as a starter, and compiled a win–loss record of 70–63 with a 3.38 ERA, 788 strikeouts, and 147 saves.

After his playing career ended, he returned to Puerto Rico, where he operated a construction business and later owned a cattle ranch.

[1] He was seventh of eight children born to Dinicio, a worker in a sugar cane factory, and Dominga, a housekeeper.

"[5] Hernández recalled that the lack of playing time caused him to lose rhythm, adding: "I was struggling.

He was used exclusively in relief, lowered his ERA to 3.00 and tallied 54 strikeouts and 10 saves, the latter being another career high to that point.

[1] Fellow relief pitcher Bill Campbell called him "one of the most professional men I've been around" and someone who gives 150% and who "you'll never get an excuse from.

"[5] Hernández gave partial credit to advice he received from Juan Pizarro while pitching in the Puerto Rican Winter League during the off-season.

[1] On May 22, 1983, the Cubs traded Hernández to the Philadelphia Phillies in exchange for pitchers Bill Johnson and Dick Ruthven.

[1] On July 3, he entered a game against the New York Mets in the eighth inning and tied the National League record by striking out six consecutive batters.

[1] Interviewed late in the season when he was batting .462, he said, "I'm not gonna say I'm a good hitter, but I make contact.

"[11] The Phillies compiled a 90–72 record, defeated the Los Angeles Dodgers to win the National League pennant, and lost to the Baltimore Orioles in the 1983 World Series.

Hernández appeared in three games during the World Series, compiling a 0.00 ERA and striking out four batters in four hitless innings pitched.

"[12] On March 24, 1984, the Phillies traded Hernández to the Detroit Tigers with Dave Bergman for Glenn Wilson and John Wockenfuss.

[13] Upon arriving at the Tigers' spring training facility, Hernández expressed eagerness to help the team in any way he could: "If they want me to come in from the bullpen, I'll do it.

It was not until September 27 that he failed to capitalize on a save opportunity, allowing a run-scoring sacrifice fly against the New York Yankees.

[16] Bill McGraw of the Detroit Free Press described Hernández as "truly the missing link, the key element the Tigers needed to nudge an already good ball club over the thin line separating parvenu from pennant contender.

Hernández learned the screwball from Mike Cuellar during the off-season in Puerto Rico prior to the 1983 season.

[21] Sports Illustrated noted that the contrast between the cutter and the screwball "set up righthanded batters to be jammed (cut fastball) or pitched away (scroogie).

[22] The four-year extension was worth an estimated $4.65 million and made Hernández the highest paid player in team history.

[1] As Hernández's performance declined, Detroit fans and sports writers were critical of the highly-paid pitcher.

"[24] The following March, Hernández dumped a bucket of ice water on Albom at spring training in Florida.

[1] In the spring of 1989, Hernández pitched well and, after a rocky relationship in which he had asked to be traded, expressed a desire to remain in Detroit for the remainder of his career.

[28] In the final year of his contract with the Tigers, elbow soreness sidelined Hernández for a portion of the season.

At age 34, Hernández appeared in his last major-league game on August 18, 1989, giving up two earned runs in one inning.

[1] In 1990, after undergoing arthroscopic surgery on his left elbow, Hernández attended spring training with the Oakland Athletics.

He said at the time that the comeback was not about money but because of his love of baseball, adding, "My spirit said I hadn't finished my career yet.

"[36] In one exhibition game appearance, Hernandez threw six pitches in one inning, retiring three Atlanta Brave batters on two fly balls and a groundout.

Defensively, he was better than average, committing only four errors in 231 total chances in 1044.2 innings pitched for a good .983 fielding percentage.

[1] After his playing career ended, Hernández owned and operated a steel construction business in Puerto Rico.

[40][21] On April 4, 2019, Hernández returned to Detroit to throw the ceremonial first pitch at the Tigers 2019 home opener.