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 major league debut was on March 31, 1998, and he became known for being a left-handed specialist reliever for the Tigers. He finished with an impressive number of appearances (88) which led the American League in that category.  Although he fell short of the league record by two appearances, his total still set a new rookie record.