A native of Jamestown in Bienville Parish in north Louisiana, Smith was scouted by Buck O'Neil and was selected by the Chicago Cubs in the 1975 MLB draft.

[4] After his playing career, Smith worked as a pitching instructor in Minor League Baseball for the San Francisco Giants.

Smith attended high school in Castor, Louisiana, where his favorite sport was basketball; he did not play on the baseball team until he was a junior.

[10] Smith made his major league debut with the Cubs, who were struggling to a last-place finish,[11] on September 1, 1980,[12] against the Atlanta Braves.

[15] His first major league save came on August 29,[15] when he recorded the final five outs of a 3–1 Cubs win over the Los Angeles Dodgers.

[14][15] During the 1982 season, closing for the Cubs was shared between Smith, Willie Hernández, Bill Campbell and Dick Tidrow, each of whom finished at least 25 games while registering 17, 10, 8, and 6 saves, respectively.

[12] Smith also collected his first MLB hit,[12] coming on July 5 against Atlanta,[20] a second-inning home run off of Phil Niekro.

[22] Years later, Smith credited Jenkins with simplifying his delivery, introducing him to the slider and forkball, and teaching him how to set up hitters.

[29] His overall 1.65 ERA for the season proved to be the lowest of his major league career,[14] nearly two runs better than the NL average of 3.63,[30] and he also posted a career-best 1.074 WHIP.

[31] Smith was selected to his first All-Star Game,[14] allowing two runs (one earned) on two hits in an inning of work as his NL team lost the 1983 mid-summer classic to the AL, 13–3.

[41] One player told writers Bruce Nash and Allan Zullo for their book, Baseball Confidential, that one of the most daunting sights in the majors was Smith throwing "pure gas from out of the shadows" of Wrigley Field,[42] which did not have lights at the time.

[2][44] On December 8, Smith, the team's career leader in saves,[45] was traded to the Boston Red Sox for pitchers Al Nipper and Calvin Schiraldi.

[46] While Smith registered nearly 300 saves after the trade,[14] Nipper only pitched in 31 more major-league games,[47] while Schiraldi was out of baseball before age 30.

[59][60] On May 4, the Red Sox chose to bolster their offense and traded Smith to the St. Louis Cardinals for outfielder Tom Brunansky.

[61] Overall in his two-plus seasons in Boston, Smith had appeared in 139 games while collecting 58 saves; in 168+2⁄3 innings pitched he struck out 209 batters.

In the strike-shortened campaign, Smith recorded 33 saves with a 3.29 ERA and captured his third (and final) Rolaids Relief Man Award.

[67] After filing for free agency again, Smith signed a two-year contract with the California Angels for over $2.5 million while the strike was still in progress.

[14][94] Early in the 1996 season, Smith spent time on the disabled list following offseason surgery—he had torn a tendon in his right knee while on a hunting trip—and second-year pitcher Troy Percival established himself as the Angels' closer.

[10][96] Upon his return to the Angels, Smith was unhappy with an inconsistent role, commenting, "I could write a movie about the past few weeks... but it would have to be a cartoon.

[100] Smith assumed setup duty for the Reds as closer Jeff Brantley was en route to a career-high 44 saves.

[105] Despite his retirement announcement, the Kansas City Royals signed Smith as a free agent[106] and invited him to spring training for 1998.

[14] Two years after his retirement in 1998, Smith went to work as a roving minor league pitching instructor for the San Francisco Giants.

Giants director of player personnel, former teammate Dick Tidrow, along with the manager of the Double-A Shreveport Captains, Jack Hiatt, offered the job to Smith, who gladly agreed, since it was in his hometown.

[113] For the 2009 World Baseball Classic, Smith returned as a coach for South Africa;[114] the team was again eliminated during pool play, losing both of their games.

"[23] Following Smith's retirement, there was speculation on his chances of becoming a member of the Hall of Fame,[116][117][118] while more generally "debate continues to rage over how to properly value reliever contributions.

"[119] At the time that Smith retired, only Hoyt Wilhelm and Rollie Fingers had been inducted to the Hall of Fame primarily for their relief pitching, in 1985 and 1992, respectively.

[125] Smith started his career earning multiple-inning saves, but the strategy in baseball for closers changed, and he was later used as a one-inning pitcher.

[129] In July 2006, at Sutter's induction to the Hall, Smith talked with reporters about his chances for election, commenting that he was puzzled that he had not yet been selected: "This confuses the hell out of me.

[131] After not being elected by the BBWAA, Smith was later selected for consideration by the 16-member Today's Game Committee as part of 2019 Baseball Hall of Fame balloting.

[149] Along with Smith and Baines, the Hall inducted BBWAA-electees Roy Halladay, Edgar Martínez, Mike Mussina, and Mariano Rivera.