At age 24, he broke into the big leagues on April 19, 1901, with the Boston Beaneaters. Crolius served as the team's fourth outfielder, playing mostly right field, where he backed up Jimmy Slagle. In 1901, his rookie year, he held a batting average of .240 with 1 home run and 13 RBIs. On July 22, 1901, Crolius had four hits which led to three runs scored in a 16–3 win over the Chicago Cubs.
In 1898 Fred Crolius was the captain of the Dartmouth football team. He was considered one of the best halfbacks in the game, but received little notice from the media, since Dartmouth was historically seen as having a weak football program.[3]
In 1901 as a member of the Homestead Library & Athletic Club, located near Pittsburgh, Crolius served as the team's halfback. That year, he scored the tying touchdown against the Blondy Wallace's Philadelphia Athletic Club. Homestead won the game 6–5; touchdowns were worth five points in 1901.[4]
In 1902, Crolius served as a halfback on the Pittsburgh Stars, a member of first National Football League that was suspected of being financed by baseball's Pittsburgh Pirates.[5] During the 1902 season, the Stars won the league championship.[1]
Coaching career
Baseball
After his playing career, Crolius served as the coach the Villanova Wildcats baseball team from 1905 until 1911. While with Villanova, acquired a 116–45–5 record.[6] He also served as the manager of the Lancaster Red Roses, where he guided the team to a 70–58 record in 1906.[7]
Football
In 1899, he also served as the head coach for the Bowdoin College football team. He guided Bowdoin to a 2–6 record.[8] In 1902, Crolius was the head coach of the Pittsburgh Panthers football team. That year the team racked up a 5–6–1 record.[9] Crolius then coached the Villanova Wildcats to an 18–38–5 record between 1904 and 1911.