Louie James Kelcher was more interested in playing baseball on the playing fields of Beaumont, Texas, but his considerable size and athletic ability eventually led him to football. He played for the French High School Buffaloes and then accepted a scholarship from Southern Methodist University. 
 
His senior year (1974), Kelcher had 22 quarterback sacks and was named a consensus All American and Southwestern Conference Defensive Player of the year. Kelcher was drafted in 1975 by the San Diego Chargers. In 1977 he led the team with 99 tackles and recorded 11 quarterback sacks, earning his first Pro Bowl berth.
 
Louie missed all but 3 minutes of the 1979 season with a serious knee injury but came back strong in 1980. He had 20 tackles and one sack against Oakland in the AFC Championship game, winning a starting spot with the AFC team in the Pro Bowl for the second time.
 
In 1981, Kelcher led the team's defensive linemen with 109 tackles; he also recorded five sacks. He was named second-team All-Pro at his position by the Associated Press and to the second team All-AFC by United Press International. Kelcher led the Chargers' defensive linemen with the best percentage of tackles to play, started 7 of 8 games, and posted 38 tackles in regular and post-season play in 1982. He started 90 out of 92 games with the team and had a career total of 39 sacks for 325 yards. 

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The Chargers traded him to the San Francisco 49ers in March 1984. Kelcher had wanted to play again, but not with San Diego. In his final NFL season, the 49ers won Super Bowl XIX. 

Kelcher was among the first NFL defensive linemen to weigh 300 pounds. He was inducted into the Chargers Hall of Fame in 2003 and the Breitbard Hall of Fame in 2006. He was also named to both the Chargers' 40th and 50th-anniversary teams. Kelcher received first-team honors on the All-Southwest Conference football team of the 1970s, and he was inducted into the Southern Methodist University Hall of Fame in 2012. He is a member of the Museum of the Gulf Coast, Sports Hall of Fame.
 
In years past, Kelcher has been heavily involved in working for the San Diego area American Cancer Society.