[1] Twice a 20-game winner (including a 25–13 season in 1907), Killian's career earned run average (ERA) of 2.38 ranks 26th best in major league history.

He played independent baseball in Racine and worked in a planing mill where he was "receiving $1.25 per day for ten hours of hard manual labor.

"[3] Killian began playing professional baseball in the spring of 1902 with the Rockford Red Sox of the Three-I League for a salary of $75 per month.

[1] In January 1904, Killian was traded by the Naps with Jesse Stovall to the Detroit Tigers for Billy Lush.

[5] As proof that his 1904 win–loss record was not indicative of his talents, Killian battled Cy Young in one of the most remarkable pitching duels in history on May 11, 1904.

He was suspended after a series of incidents in which he destroyed a telephone and various articles of furniture in the clubhouse in a rage, showed up on multiple occasions not "in condition to play ball", and trouble under the grandstand in which officers had to be called to prevent Killian from going on the field.

[10][11][12] Between September 19, 1903, and August 7, 1907, a span of nearly four years and 1,001 innings, he did not allow an opposing batter to hit a home run.

[14] Killian's 8.0 wins above replacement (WAR) in 1907 was the highest of any player in the American League at any position, higher even than teammate Ty Cobb.

Unfortunately, Killian's arm was worn out for the post-season, and he pitched only four innings in relief with no decision during the 1907 World Series against the Chicago Cubs.

He also started one game in the 1908 World Series, giving up five hits, three walks, and three earned runs in 2+1⁄3 innings.

[1] After seven seasons in a Detroit uniform, he was sold to the Toronto Maple Leafs of the International League on August 2, 1910.

[19] At the time of his release, the Detroit Free Press wrote: "Gameness has been one of Killian's chief assets.

He has the reputation of being as nervy a pitcher as ever stepped to the slab and repeatedly won games when his arm was out of condition through sheer pluck.

Killian also is the possessor of a great pitching head, studying the opposing batsmen and preying upon their weaknesses.