Over an eighteen-year career spanning six American League teams, he was a four-time All-Star and won a World Championship with the 1968 Tigers.

He had a career-high 36 home runs in 1968, a pitcher's year in which Detroit won the World Series; he finished second in the AL to Frank Howard in homers, slugging and total bases.

In order to combine Horton's offensive power with a good defense, manager Mayo Smith moved regular center fielder Mickey Stanley to shortstop as a replacement for Ray Oyler, who was benched because of his paltry .135 batting average.

He tried to score on Julián Javier's single, but chose not to slide; Horton's throw reached catcher Bill Freehan on one bounce to beat Brock on a close play.

While chasing a fly ball, Kaline collided with outfielder Jim Northrup and fell onto the warning track.

Realizing what happened, Horton rushed over and pried opened Kaline's mouth, clearing his airway and likely saving his life.

[9][10] In 1979 with the Mariners, he was again named the AL's Outstanding Designated Hitter after hitting .279 with 29 HR and a career-high 106 RBI, and he received The Sporting News Comeback Player of the Year Award as well.

On June 5, against the Tigers against John Hiller, he hit what seemed to be his 300th career home run, but it struck a speaker hanging from the roof of the Kingdome and bounced onto the field for a single; he would collect number 300 the next day against Jack Morris.

His record of 646 at bats was broken by Alex Rodriguez in 1998; Horton remains one of only four Mariners to have played the full 162 games in a season.

He was traded back to the Rangers from the Mariners along with Rick Honeycutt, Leon Roberts, Mario Mendoza and Larry Cox for Richie Zisk, Jerry Don Gleaton, Rick Auerbach, Ken Clay, Brian Allard and minor-league right-handed pitcher Steve Finch in an 11-player blockbuster deal on December 18, 1980.

[15] Then-Governor Jennifer Granholm said of the proclamation: Willie Horton is one of those rare baseball players who doesn't need a diamond to truly sparkle and shine—he's a star on and off the field.

[18] Since 2003, Horton has served as a Special Assistant to Tigers President/CEO/General Manager, originally Dave Dombrowski, followed by Al Avila, and currently Scott Harris.

Former Tigers teammate Al Kaline also held this position, and the two threw out the first pitch of the 2006 World Series at Comerica Park.