During his prime, Clark was one of the most feared right-handed hitters in the National League, winning the Silver Slugger Award in 1985 and 1987.

Clark began his minor league baseball career in 1973 with the Great Falls Giants where he played the outfield and third base and had a 0-2 record in 5 games as a pitcher.

[1] Clark started his major league career with the San Francisco Giants in 1975 as a right fielder and the youngest player in 1975 (19).

[3] He had a rift with manager Frank Robinson, and some members of the Giants front office thought Clark took too long to recover from injuries.

[3] On February 1, 1985, Clark was traded to the St. Louis Cardinals for shortstop José Uribe, pitcher Dave LaPoint, and first basemen-outfielders David Green and Gary Rajsich.

His three-run home run against the Los Angeles Dodgers in game 6 of the 1985 NLCS was the pennant-clinching hit for the Cardinals.

Umpire Don Denkinger's notorious controversial call in Game 6 came from Clark's throw to Todd Worrell at first.

Clark again led the Cardinals to the World Series that year, although an ankle injury limited him to one at-bat in the postseason.

[4][5] After the 1988 season, the Yankees traded Clark to the San Diego Padres with Pat Clements for Lance McCullers, Jimmy Jones, and Stan Jefferson.

In 1990, he feuded with All-Star teammate Tony Gwynn, who was widely respected by his peers and known as one of the most dedicated players in baseball.

[7][8][9] Clark called him selfish and stated that Gwynn should be swinging with runners in scoring position instead of bunting and protecting his batting average.

"[14][15] Clark returned to the American League in 1991, signing with the Boston Red Sox for three years over the Padres' offer of only one.

After hitting only five home runs in a truncated 1992 season, Clark was waived by Boston in February 1993 and was signed to a minor league contract by the Montreal Expos during 1993 spring training.

[21] Pujols responded by threatening Clark and WGNU with a defamation lawsuit, and vehemently denied that he had ever used PEDs.

InsideSTL Enterprises, who owned WGNU's weekday airtime through a time brokerage agreement,[22] cut ties with Clark and Slaten after only seven shows.