John Spencer "Big Joe" Curtis[2][3] (November 14, 1882 – January 29, 1972) was an American football player and coach.

In his four seasons as the starting left tackle for the Michigan Wolverines, the team compiled a record of 37–2–1, won two national championships and outscored opponents by a combined total of 1,699 to 60.

Curtis later served as the head football coach at Tulane University from 1907 to 1908 and at the Colorado School of Mines in 1909.

He started all twelve games at left tackle for the Michigan team that finished the season with a record of 11–0–1, outscored opponents 565–6, and has been retrospectively declared National Champions.

[5] In 1904, Curtis started all ten games at left tackle for the Michigan football team that compiled a 10–0 record, outscored opponents 567–22, and has been retrospectively declared national champions.

On the offense he has developed into one of the best ground gainers on Yost's eleven, and has been most effective in disposing of his opponents when his team has had possession of the ball.

'"[10] Curtis was considered one of the best defensive players in the West, but he was also a leading ball-carrier and kicker for Michigan on offense.

[12] A newspaper account of the incident reported that, after Eckersall had gotten the punt safely away, Curtis, who had broken through, "came down on the little maroon like a whirlwind, knocking him down.

"[14] The selection of Curtis was reported to be "peculiarly pleasing to Ann Arbor's students ... because they think that his disqualification in the Chicago match was a great injustice and mistake.

"[4]In 1906, Yost undertook what was referred to in the press as a "startling shift" in moving Curtis to the left end position.

One sports writer referred to Curtis as a "mastodon," and noted that, although he "carries something like an eighth of a ton of beef and brawn whenever he moves," he also had "the speed of a quarter horse.

[26] In 1909, Curtis retired as Tulane's coach and announced plans to enter business in his home state of Colorado.

[28] In November 1909, a Colorado Springs newspaper reported that Curtis had injected "more ginger" into the school's playbook and had "planned a number of new and spectacular formations.

[30] After retiring from coaching, Curtis lived in Denver and was called upon to referee important inter-collegiate football games.