There was once a time in baseball where it was very common to see the team manager in uniform out on the field actually playing alongside their teammates. In MLB, it hasn't happened since Pete Rose took the field and the helm for the Reds in 1984. It was, however, quite normal in the earlier days of baseball, as it was a way to save money by paying one less person: Maybe Jeffrey Loria not only has an appreciation for art, but also for money-saving bits of history.
The very first manager of the team that would become the Boston Red Sox was one such person. His name was Jimmy Collins, and today he's regarded as more or less the prototypical third baseman, the individual who codified the position for future generations. He also served as a player-manager for the team for several years, leading them to victory in the first-ever World Series in 1903 and the American League pennant in 1904. Collins was elected -- as a player -- to Cooperstown by the Old Timers Committee in 1945, cementing his legacy as a third baseman.
He was a solid hitter, with a lifetime average of .294 and a respectable 65 home runs in the Dead-ball Era. However, he's best remembered today as a fine third baseman, establishing the position as the one to play bunts down the third base line (previously a role of the shortstop, a rather clumsy sort of thing).
Collins spent the vast majority of his 14-year career in Boston, first starting with the Beaneaters (now the Braves) in 1895. He spent part of that season on loan to the Louisville Colonels, but returned to Boston for the next campaign and remained with the Beaneaters up through 1900. He was one of Boston's representatives in the Players Protective Association that year, although after attending two meetings he realized that a compensation increase would not be possible in his current situation without a move. Ever the savvy businessman (he ran a real estate business building family housing in his hometown of Buffalo during the off-season and his retirement), he knew what he had to do.
In 1901, still looking for a salary increase and not finding one in the National League, he made his fated jump to the American League, joining the Americans as their manager, captain, and third baseman for an at the time phenomenal salary of $3,500 a year for three years. This led to a rift between Collins and the owner of the Beaneaters, Arthur Soden, who made a strong (in his opinion) effort to retain Collins. The two traded words, and Collins explained his league-jumping to readers of the Boston Globe in 1901, saying, "I have given the National league people my best efforts for several years past and often asked them for more money, knowing that I was worth it, but until now they have turned a deaf ear to all my requests. …I saw a chance to better myself and took it."
Collins actually slotted in well as a manager, applying his business acumen to his managerial style and fostering a camaraderie among his players by playing right alongside them at third base. The team came in second in 1901 and third in 1902, but in 1903 Collins led the team to its first-ever American League pennant. The owners of the Americans and the Pirates had agreed to play an interleague postseason series, but the agreement only led to shared revenue for the team owners and left the players out. Collins saw an opportunity and jumped in:
The agreement provided for the owners to share revenue from the games, but did not include a provision to pay the ballplayers. Since the contracts of the Boston players expired at the end of September, Killilea [the Americans' owner] had foolishly entered into a contract to play a postseason series without securing the services of the Boston ballplayers. Collins exploited Killilea’s poor business judgment to negotiate a great deal for the ballplayers. They got not just 75 percent of Boston’s portion of the shared revenue under the World Series agreement, but 75 percent of all of Boston’s net revenue from the series.
The Americans won what became the first World Series in 1903 4 games to 3, securing the first championship ever for the Red Sox franchise. The team returned in 1904 and continued their pennant-winning ways, barely beating out the New York Highlanders (who would go on to become the most intensely hated sports team in Boston) for the title, but the New York Giants, the National League pennant winners that year, declined to play a postseason series. The World Series would become a regular fixture in 1905.
Amidst all sorts of controversies regarding his partial ownership in the team and showdowns with new team president John I. Taylor, Collins remained with the team until the beginning of the 1907 season, when he was shipped off to the Philadelphia Athletics for John Knight. He was let go by the A's after his numbers slumped in 1908, ending his major league career. Collins played three minor-league seasons before officially retiring and focusing on his business ventures and family full-time.
Overall, despite only being with the team for a little over six seasons, it's clear that Collins left his mark on Red Sox history. He negotiated player contracts, managed the team to its very first World Series title (and two pennants total), and had a major impact on the culture of the club, including attracting the Royal Rooters over to support the team, a major factor in the success story of 1903. Although he's not remembered as well as another player-manager in Red Sox history, Joe Cronin, he certainly deserves to be celebrated for his efforts and his skills at third base as well.
For more on Jimmy Collins's playing career, you can examine his all-time stats at Baseball Reference here. If you'd like to learn more about the man himself and his business dealings, his SABR article (which I've cited a few times here) is an excellent resource, too.