[5] On August 9, 1906, Willett was purchased from Wichita by the Detroit Tigers, and became the first Western Association player to make it with a major league club.

[5][6] Originally scheduled to remain with Wichita through the end of the 1906 season, the Tigers asked in late August that he report early.

[2] In 1907, Willett saw limited action with the Tigers, appearing in 10 games, six as a starter, and compiled a 1–5 record with a 3.70 ERA in 48+2⁄3 innings pitched.

[2] Willett became a regular starting pitcher for the 1908 Detroit Tigers team that won the American League pennant.

He also appeared in two games as a relief pitcher in the 1909 World Series, giving up no earned runs and three hits in 7+2⁄3 innings pitched against the Pittsburgh Pirates.

[2] In January 1914, Willett signed a contract to play for Mordecai Brown's St. Louis Terriers in the Federal League.

[8] The Terriers finished in eighth place in the Federal League in 1914, and Willett compiled a career-worst 4–17 record with a 4.27 ERA in 27 games.

[2][9] Willett was an excellent fielding pitcher, consistently achieving a range factor in excess of the league average.

His range factor of 3.38 in 1912 was a remarkable 1.43 points higher than the league average of 1.95 — meaning Willett got to nearly twice as many batted balls as the typical pitcher of his era.

[2] Detroit trainer Harry Tuthill later recalled, "Ed always could hit, but he gave the fans a real thrill one afternoon at old Bennett Park, by clouting two home runs.