After retiring from football, Agase worked as an assistant coach for the Dallas Texans and, after a brief return to playing for the Baltimore Colts, Iowa State University.

[2][3] In a 1942 game against the University of Minnesota, Agase scored two touchdowns for the Fighting Illini, becoming only the second guard in college football history to accomplish that feat.

[2] The first touchdown came in the second quarter, when Agase stripped the ball from Minnesota's Bill Daley and ran it back 35 yards.

[6] Purdue had won just one Big Ten Conference game the previous year, but the influx of trainees including Agase led to a reversal of fortune in 1943.

[6] Coached by Elmer Burnham, the Purdue Boilermakers won all of their games that year and were named Big Ten co-champions.

[10] Agase returned to Illinois in 1946 and rejoined a Fightining Illini team that posted an 8–2 record and was ranked fifth in the nation in the AP Poll at season's end.

[12] Agase was named an All-American for a third time, and received the Chicago Tribune Silver Football as the most valuable player in the Big Ten.

[9][10] Agase had been selected by the Green Bay Packers in the 1944 NFL draft, but military service delayed his professional career.

Although Green Bay still held the rights to him when he graduated from college, Agase instead signed in 1947 with the Los Angeles Dons of the new All-America Football Conference (AAFC).

[16][17] Led by quarterback Otto Graham, fullback Marion Motley and ends Dante Lavelli and Mac Speedie, Cleveland won the championship again in 1948, posting a perfect 14–0 record and beating the Buffalo Bills in the title game.

"[22] Before the 1952 season, the Browns traded Agase to the Dallas Texans, a newly formed team set to start play that year.

[24][25] Agase came out of retirement briefly after the Texans disbanded, joining the Baltimore Colts and playing as a linebacker for the 1953 season.

[30] When Parseghian was offered the head coaching job at the University of Notre Dame at the end of 1963, he recommended Agase as his replacement.

[32] In 1970, however, the team finished with a 6–4 record, taking second place in the Big Ten Conference, and Agase was named the national coach of the year by the Football Writers Association of America.

[36] Agase remained active in college football by assisting Bo Schembechler as a volunteer at the University of Michigan until 1987, focusing on special teams.