In his MLB debut on June 16, 1894, Tenney had to be removed from the game in the fifth inning due to a fractured finger on his throwing hand from a foul tip.
After Tenney had his finger addressed, James Billings, an owner of the Beaneaters, offered him a contract worth US$300 a month from that day.
Tenney, later writing about the day, stated:
I thought they were trying to have a little joke with me, and I concluded that I could do a little kidding myself.
So I thought I would call their bluff by asking for some advance money.
I screwed up my courage and asked Mr. Billings whether, if I signed the contract at once, I could get some advance money.
He asked how much I wanted, and I thought I would mention a big sum in order to call their bluff good and strong.
So I said $150.
He consulted with Mr. Conant, another Director, and said that I could have the money all right, and asked me how I would like to have it– cash or check. [...]
I replied that I would take half cash and then half in check, and immediately he wrote out a check for $75, counted out $75 in cash, shoved the contract over to me to sign, laying the cash and check beside it.

— Fred Tenney, The New York Times
He returned to the team a month later, and finished the year batting .395 in 27 games.
The following season, Tenney moved to the outfield due to an erratic throwing arm behind the plate, according to manager Selee.
For the season, he hit .272 in 49 games, while also playing minor league baseball for the New Bedford Whalers.
In 1896, Tenney again caught and played outfield; offensively, however, Tenney hit .336 in nearly double the games from the previous year (88) despite playing in the minors for the Springfield Ponies.

In 1897, Tenney moved to first base to replace the aging Tom Tucker.
According to Alfred Henry Spink, within two weeks of the move it was evident that Tenney had become "one of the finest first sackers that the game [had] ever seen."
On June 14, 1897, in a game against the Cincinnati Reds, Tenney turned the first 3-6-3 double play in MLB history.
Offensively, Tenney led MLB in plate appearances (646) and tied Duff Cooley, Gene DeMontreville, and George Van Haltren for the lead in at bats (566) as the Boston club became National League (NL) champions with a 93–39 record.

Boston again won the NL in 1898 while Tenney hit .328 with 62 RBIs.
In 1899 he collected 209 hits, fifth most in MLB, and recorded 17 triples, good for fourth best in MLB.
In 1900 Tenney, at age 28, batted .279 over 112 games played.
He began a streak of seven consecutive seasons where he led the NL in assists in 1901; he holds the record for most seasons leading a league in assists, with eight, including one in 1899.
He was suspended for ten games for fighting Pittsburgh Pirates manager Fred Clarke in May 1902, and finished the 1902 season with the second most sacrifice hits (29) in the majors, to go along with a .315 average.
Throughout the 1901–1902 seasons, Tenney received contract offers worth up to $7,000 ($206,248 in 2017) from St. Louis, Cleveland, and Detroit; Tenney, however, decided to remain in Boston, and was named captain of the club in 1903.
For the season, he hit .313, with 41 RBIs and three home runs, as he led his team in walks (70) and had the best on-base percentage mark (.415) on the squad.
In 1904, Tenney again led his team in walks and on-base percentage, as he tied for the team lead in runs with Ed Abbaticchio.

He was named manager of the team in 1905, but did not receive additional pay; he was, however, offered a bonus if the team didn't lose money.
In 1905, Tenney tried to sign William Clarence Matthews, an African-American middle infielder from Harvard University, to a contract.
Tenney later retracted his offer due to pressure from MLB players.
Defensively, he led the majors in errors committed by a first baseman and finished second in most putouts for any position.
Tenney led the 1906 Beaneaters to a 49–102 record.
For the second straight year, the Boston team lost more than 100 games.

After a 158–295 record as manager, on December 3, 1907, Tenney
In his MLB debut on June 16, 1894, Tenney had to be removed from the game in the fifth inning due to a fractured finger on his throwing hand from a foul tip. After Tenney had his finger addressed, James Billings, an owner of the Beaneaters, offered him a contract worth US$300 a month from that day. Tenney, later writing about the day, stated:
I thought they were trying to have a little joke with me, and I concluded that I could do a little kidding myself. So I thought I would call their bluff by asking for some advance money. I screwed up my courage and asked Mr. Billings whether, if I signed the contract at once, I could get some advance money. He asked how much I wanted, and I thought I would mention a big sum in order to call their bluff good and strong. So I said $150. He consulted with Mr. Conant, another Director, and said that I could have the money all right, and asked me how I would like to have it– cash or check. [...] I replied that I would take half cash and then half in check, and immediately he wrote out a check for $75, counted out $75 in cash, shoved the contract over to me to sign, laying the cash and check beside it.
— Fred Tenney, The New York Times
He returned to the team a month later, and finished the year batting .395 in 27 games. The following season, Tenney moved to the outfield due to an erratic throwing arm behind the plate, according to manager Selee. For the season, he hit .272 in 49 games, while also playing minor league baseball for the New Bedford Whalers. In 1896, Tenney again caught and played outfield; offensively, however, Tenney hit .336 in nearly double the games from the previous year (88) despite playing in the minors for the Springfield Ponies.
In 1897, Tenney moved to first base to replace the aging Tom Tucker. According to Alfred Henry Spink, within two weeks of the move it was evident that Tenney had become "one of the finest first sackers that the game [had] ever seen." On June 14, 1897, in a game against the Cincinnati Reds, Tenney turned the first 3-6-3 double play in MLB history. Offensively, Tenney led MLB in plate appearances (646) and tied Duff Cooley, Gene DeMontreville, and George Van Haltren for the lead in at bats (566) as the Boston club became National League (NL) champions with a 93–39 record.
Boston again won the NL in 1898 while Tenney hit .328 with 62 RBIs. In 1899 he collected 209 hits, fifth most in MLB, and recorded 17 triples, good for fourth best in MLB. In 1900 Tenney, at age 28, batted .279 over 112 games played. He began a streak of seven consecutive seasons where he led the NL in assists in 1901; he holds the record for most seasons leading a league in assists, with eight, including one in 1899. He was suspended for ten games for fighting Pittsburgh Pirates manager Fred Clarke in May 1902, and finished the 1902 season with the second most sacrifice hits (29) in the majors, to go along with a .315 average. Throughout the 1901–1902 seasons, Tenney received contract offers worth up to $7,000 ($206,248 in 2017) from St. Louis, Cleveland, and Detroit; Tenney, however, decided to remain in Boston, and was named captain of the club in 1903. For the season, he hit .313, with 41 RBIs and three home runs, as he led his team in walks (70) and had the best on-base percentage mark (.415) on the squad. In 1904, Tenney again led his team in walks and on-base percentage, as he tied for the team lead in runs with Ed Abbaticchio.
He was named manager of the team in 1905, but did not receive additional pay; he was, however, offered a bonus if the team didn't lose money. In 1905, Tenney tried to sign William Clarence Matthews, an African-American middle infielder from Harvard University, to a contract. Tenney later retracted his offer due to pressure from MLB players. Defensively, he led the majors in errors committed by a first baseman and finished second in most putouts for any position. Tenney led the 1906 Beaneaters to a 49–102 record. For the second straight year, the Boston team lost more than 100 games.
After a 158–295 record as manager, on December 3, 1907, Tenney
Fred Tenney