Kennedy was born in La Mesa, California to John and Holly Kennedy. He had an older brother, John Kennedy Jr., and a younger sister, Bettianne Kennedy. Kennedy played Little League in El Cajon, California. He was a member of the 1991 El Cajon American Little League team that won the Southern California Little League championship. The team was eliminated after a first-round 3-1 loss to Kahulia East Maui in the West Region Tournament in San Bernardino. He graduated from El Cajon Valley High School, where he played baseball as well as basketball, volleyball and football. He attended Grossmont College before entering the major league draft.
Kennedy made his Major League debut on June 6, 2001, becoming the first lefthander to start a game for the Devil Rays in 219 games. He finished 7-8 in 20 starts for the Devil Rays. In his second season, he pitched in 30 starts going 8-11 while throwing 5 complete games for the Devil Rays. In 2003, he was named the Opening Day starter for the Devil Rays after having an abysmal spring training. He made 22 straight starts before being relegated to the bullpen after suffering an arm injury in. He had pitched in 72 consecutive starts for the Devil Rays before being moved to the bullpen. He recorded his first career save on September 10, 2003 against the Blue Jays, pitching three scoreless innings.
Colorado Rockies
Traded to the Colorado Rockies before the season, Kennedy became the first Rockies starter to have a sub 4.00 earned run average, setting a franchise record with a 3.66 ERA while going 9-7 for the Rockies. In 2005, Kennedy struggled as a starter for the Rockies, going 4-8 with a 7.04 ERA.
Oakland Athletics
On June 5, 2005, the A's showed interest in Kennedy. On July 13 of that year, Kennedy, along with pitcher Jay Witasick, was traded by the Rockies to the Oakland Athletics for outfielderEric Byrnes and minor league infield prospect Omar Quintanilla. Kennedy pitched in the bullpen for Oakland before being pressed into the starter role in September when Rich Harden was injured. Kennedy went 1-5 as a starter for Oakland, and finished the year with a 4-5 record and a 4.70 ERA in the American League. Kennedy pitched well in a middle relief role in Oakland's bullpen in 2006, with a record of 4-1 and a 2.31 ERA. Unfortunately, his role was diminished as he missed three months with shoulder and biceps injuries. Despite struggling in spring training with an ERA above 11.00, Kennedy was named the fifth starter for the Athletics at the start of the season. Through June 2 he compiled a 1-4 record with a 3.3 ERA in 62 innings. He was ineffective afterwards and was placed on waivers.
Arizona Diamondbacks
Kennedy was claimed by the Arizona Diamondbacks on August 4 after being placed on waivers by the Athletics. He was designated for assignment on August 15 after allowing 7 runs in 3 games and was released by the Diamondbacks.
Toronto Blue Jays
He signed a minor league contract with the Toronto Blue Jays on August 28 and was called up to the major league team on September 2. He pitched in nine games, all in relief, for the Blue Jays in the final month of the season and went 1-0 with a 5.14 ERA. He became a free agent after the season.
Scouting
Kennedy had a bevy of pitches at his disposal, featuring a low-90s four-seam fastball, an 88–90 MPH two-seam fastball, a slow curve, a diving slider and, possibly his second-best pitch after his fastball, a deceptive changeup. His powerful delivery was at the 3/4-sidearm slot, which made his pitches particularly hard for left-handed batters to pick up. He was also very effective against right-handed batters. After struggling a little as a spot-starter for the Athletics, he pitched well in the bullpen in 2006, holding his opponents to a.254 batting average and going 4-1 with a 2.31 ERA.
Death
On November 23, 2007, Kennedy was in Florida to be the best man at the wedding of a friend. He woke up in the middle of the night and collapsed at the home of his in-laws. He was taken to Brandon Hospital in Brandon, where he was pronounced dead. At the time of Kennedy's death, he was married to Jami Kennedy, who was pregnant with their second child On January 15, 2008, it was announced by the medical examiner that Kennedy had died of hypertensive heart disease with degeneration of the mitral valve. After Kennedy's death, Frank Thomas kept Kennedy's glove in his locker wherever he played until he retired.
