Runyan's major league debut came on March 31, 1998. He would be used as a left-handed specialist out of the Tigers bullpen, and would go on to lead the American League in appearances with 88. The 88 appearances were 2 short of the American League record, but were enough to set the record for rookies.
Runyan's debut in Major League Baseball took place on March 31, 1998. He was primarily used as a left-handed reliever for the Tigers and finished with an impressive 88 appearances, which led the American League in that category.  While he fell short of the league record by two appearances, his total still set a new rookie record.