Keefe entered the major leagues in 1880 with the Troy Trojans.
He immediately established himself as a talented pitcher, posting an astounding 0.86 ERA in 105 innings pitched, a record that still stands. (
He also posted the best Adjusted ERA+ in baseball history in 1880.)
Despite the sterling ERA, he managed but a 6–6 record, pitching in 12 games, all complete games.

In 1883, after the Trojans folded, Keefe rose to stardom with the New York Metropolitans of the American Association under manager "Gentleman" Jim Mutrie and had one of the most dominating seasons in baseball's early history.
On July 4 of that year, Keefe pitched both ends of a doubleheader against Columbus, winning the first game with a one-hitter; the second a two-hit gem.
He went 41–27 over 619 innings pitched with a 2.41 ERA and 361 strikeouts.
His 1884 campaign was almost as dominant, winning 37 games, losing 17, and striking out 334.

In 1885, John B. Day, who owned the Metropolitans and the New York Giants of the National League, moved Keefe and Mutrie to the Giants.
Here, Keefe joined future Hall of Famers Buck Ewing, Monte Ward, Roger Connor, Mickey Welch, and "Orator" Jim O'Rourke to form an outstanding team that finished with a fine 85–27 record.
Keefe went 32–13 with a 1.58 ERA and 227 strikeouts.
In 1887, Keefe sat out several weeks of the season after he struck a batter in the head with a pitch; he was said to have suffered a nervous breakdown.

He had arguably his greatest season in 1888, when he led the league with a 35–12 record, 1.74 ERA and 335 strikeouts (see Triple Crown).
He won 19 consecutive games that season, a record that stood for 24 years.
 The Giants played the St. Louis Browns of the American Association in a postseason series for the Dauvray Cup, and Keefe added four more wins to his tally.
Keefe even designed the famous all-black "funeral" uniforms the Giants wore that season.

Keefe was very well-paid for his career, yet he was a leading member of the Brotherhood of Professional Base Ball Players, an early players' union that fought for the welfare of players.
He assisted his brother-in-law Monte Ward to form the Players' League for the 1890 season.
As a co-organizer of the Players' League, he recognized that he might be financially vulnerable if the league failed to make money.
Keefe transferred ownership of his real estate assets to his mother so that they would remain safe from any legal rulings.

Shortly before the Players' League was founded, Keefe had started a sporting goods business in New York with W. H. Becannon, a former employee of baseball owner and sporting goods entrepreneur Albert Spalding.
Keefe and Becannon manufactured the Keefe ball, the official baseball of the league.
Spalding and the other NL owners fought against the new league, employing legal and financial maneuvers (such as slashing NL ticket prices) that made competition difficult.
 The Players' League folded after one season.

In the 1891 preseason, Keefe refused a salary offer of $3,000 from New York; he had earned $4,500 in the previous season.
Keefe said, "I want to play in New York, but I never will for a $3,000 salary... To tell you the truth, however, I do not think I am wanted in the New York team, and this cutting method is being pursued to keep me out."
Keefe ultimately signed with the team for a $3,500 salary.

During the 1891 season, Keefe was released by New York.
He was drawing a high salary and was not meeting the expectations of the team's leadership.
After his release, Keefe said, "I hate to leave New York, am very fond of it, and would do all in my power for New York, but what am I to do?
I have been systematically done by the New York Baseball Club... They would not let me play, and when I did get a chance, I worked under a disadvantage.
I feel that I am just as good a player as I ever was."

Keefe moved to the Philadelphia Phillies after his release from the Giants.
He retired after the 1893 season with 342 wins (10th all time), a 2.62 ERA, and 2,562 strikeouts.
His 2,562 strikeouts were a major league record at the time of his retirem
Keefe entered the major leagues in 1880 with the Troy Trojans. He immediately established himself as a talented pitcher, posting an astounding 0.86 ERA in 105 innings pitched, a record that still stands. (He also posted the best Adjusted ERA+ in baseball history in 1880.) Despite the sterling ERA, he managed but a 6–6 record, pitching in 12 games, all complete games.
In 1883, after the Trojans folded, Keefe rose to stardom with the New York Metropolitans of the American Association under manager "Gentleman" Jim Mutrie and had one of the most dominating seasons in baseball's early history. On July 4 of that year, Keefe pitched both ends of a doubleheader against Columbus, winning the first game with a one-hitter; the second a two-hit gem. He went 41–27 over 619 innings pitched with a 2.41 ERA and 361 strikeouts. His 1884 campaign was almost as dominant, winning 37 games, losing 17, and striking out 334.
In 1885, John B. Day, who owned the Metropolitans and the New York Giants of the National League, moved Keefe and Mutrie to the Giants. Here, Keefe joined future Hall of Famers Buck Ewing, Monte Ward, Roger Connor, Mickey Welch, and "Orator" Jim O'Rourke to form an outstanding team that finished with a fine 85–27 record. Keefe went 32–13 with a 1.58 ERA and 227 strikeouts. In 1887, Keefe sat out several weeks of the season after he struck a batter in the head with a pitch; he was said to have suffered a nervous breakdown.
He had arguably his greatest season in 1888, when he led the league with a 35–12 record, 1.74 ERA and 335 strikeouts (see Triple Crown). He won 19 consecutive games that season, a record that stood for 24 years.  The Giants played the St. Louis Browns of the American Association in a postseason series for the Dauvray Cup, and Keefe added four more wins to his tally. Keefe even designed the famous all-black "funeral" uniforms the Giants wore that season.
Keefe was very well-paid for his career, yet he was a leading member of the Brotherhood of Professional Base Ball Players, an early players' union that fought for the welfare of players. He assisted his brother-in-law Monte Ward to form the Players' League for the 1890 season. As a co-organizer of the Players' League, he recognized that he might be financially vulnerable if the league failed to make money. Keefe transferred ownership of his real estate assets to his mother so that they would remain safe from any legal rulings.
Shortly before the Players' League was founded, Keefe had started a sporting goods business in New York with W. H. Becannon, a former employee of baseball owner and sporting goods entrepreneur Albert Spalding. Keefe and Becannon manufactured the Keefe ball, the official baseball of the league. Spalding and the other NL owners fought against the new league, employing legal and financial maneuvers (such as slashing NL ticket prices) that made competition difficult.  The Players' League folded after one season.
In the 1891 preseason, Keefe refused a salary offer of $3,000 from New York; he had earned $4,500 in the previous season. Keefe said, "I want to play in New York, but I never will for a $3,000 salary... To tell you the truth, however, I do not think I am wanted in the New York team, and this cutting method is being pursued to keep me out." Keefe ultimately signed with the team for a $3,500 salary.
During the 1891 season, Keefe was released by New York. He was drawing a high salary and was not meeting the expectations of the team's leadership. After his release, Keefe said, "I hate to leave New York, am very fond of it, and would do all in my power for New York, but what am I to do? I have been systematically done by the New York Baseball Club... They would not let me play, and when I did get a chance, I worked under a disadvantage. I feel that I am just as good a player as I ever was."
Keefe moved to the Philadelphia Phillies after his release from the Giants. He retired after the 1893 season with 342 wins (10th all time), a 2.62 ERA, and 2,562 strikeouts. His 2,562 strikeouts were a major league record at the time of his retirem
Tim Keefe