Knott joined Milwaukee of the American Association in 1931. He was 11-9 that year and 17-12 in 1932, prompting his sale to the St Louis Browns. The 26-year-old right-hander made his debut with the Browns on April 13, 1933. He was 1-8 for the last-placed team but was 10-3 in 1934 as the Browns climbed to sixth place.

Knott was traded to the White Sox in June 1938 and joined the Philadelphia Athletics in 1941. He was 2-10 for the basement-dwelling Athletics in 1942 before entering military service on November 24 of that year.

Knott served with the Army at Camp Wolters Reception Center in Texas, before being assigned to Camp Adair, Oregon as an acting first sergeant with the 104^th “Timberwolf” Infantry Division. During the summer of 1943, Knott had plenty of opportunity to play baseball with the 104^th Timberwolves team. Home games were played at George Waters Field, formerly home of Salem in Western International League, and much of the equipment they used was made available by Mrs George Waters, owner of the Salem club. The Timberwolves won the Oregon state semipro and Pacific Northwest servicemen's titles that year.

In April 1944, Knott was first sergeant with Headquarters Company of the 104^th Division at Camp Carson, Colorado. The division was shipped to Europe later in the year and landed in France on September 7, 1944. The 104th's first combat experience occurred during the latter part of the Battle of the Scheldt – an operation in northern Belgium aimed at opening the port of Antwerp to Allied shipping. On November 6, 1944, the 104th began moving by motor convoy towards Aachen, Germany and participated in the Battle of Hurtgen Forest.