The roster for a Major league baseball team consists of a pool of 40 players. This roster of 40 is then broken down to an active player list of 25. The remaining 15 players will either be playing in the minor leagues, or on the disabled list.

The 25 player roster must be complete before August 31 of any season in order for the players to be eligible for play-off and World Series games. There is one exception for this rule in that a player on the 60 day disabled list can be replaced by another player who plays the same position, and is on the 40 man roster as of August 31.

According to the MLBPA (Major League Baseball Players Association), a labour union for MLB players:

In accordance with Major League Rule 2 (c), beginning on Opening Day of each season and ending at midnight, August 31, the Club roster limit is 25, provided that the minimum number of active players maintained by each Club be 24. If the roster is reduced below 24 then the Club shall, within 48 hours (plus time necessary for a player to report), bring its roster back to the minimum of 24. Beginning on September 1 and ending with the close of the Championship Season, the roster limit is expanded to 40. http://mlbplayers.mlb.com/pa/info/faq.jsp

NB - Please note that in the table below DL stands for Disabled List

There is much debate about which was the greatest ever Red Sox team, but fans and foes alike will admit it is between the 1915 Red Sox and the 2004 team. The 1915 Boston Red Sox Team played 151 games during the regular season, won 101 of them, lost 50, and finished in first position. They then went on to trounce the Philadelphia Phillies 4 games to 1 after dropping the first game.

This Red Sox team was so full of talent that the famous Babe Ruth couldn’t get a game in the World Series. Ruth did appear once in the Series, as a pinch hitter, but without success. Strangely enough, the 1915 Red Sox played their home games away from Fenway Park at the home of the then Boston Braves. This was initially to generate more income for the Sox, but as it turned out, the logistics of Braves Field probably contributed to their victories.

What was the core of this team would go on to win the World Series the following year and again in 1918. That was the last year that the great Babe Ruth played for the Red Sox. In 1919 Ruth would be sold to bitter rivals the New York Yankees, beginning the era of “The Curse of the Bambino” a time of drought that saw the Red Sox go without a World Series championship until 2004.

Not surprisingly it is the team that ended “The Curse of the Bambino” in 2004 that is considered by most modern day fans to be the best Red Sox team ever. After falling behind three games to nil against the Yankees in the ALCS final, the Red Sox won the next four straight to shock the Yankees and the entire Baseball world and reach the World Series. The momentum gathered in that famous victory over the Yankees propelled the Red Sox to a 4-0 sweep against The Saint Louis Cardinals in what Red Sox fans consider to be “the best season ever.”

The combination of winning the World Series and ending “The Curse of the Bambino” made sure the 2004 Sox will go down in history as perhaps the greatest combination of Red Sox talent and tenacity ever.