1871 Preview - New York Mutuals

The Mutual Base Ball Club of New York (which is how they were known - the modern day naming convention of first the city and then the nickname had not yet evolved) was founded in 1857, the year the National Association of Base Ball Players was founded. Although they were never as strong as 1860s powerhouses Excelsior of Brooklyn or Atlantic of Brooklyn, they did win the Association championship in 1868, and with the advent of openly paid ballplayers (most sources suggest that star players were secretly paid throughout the 1860s) they were well-equipped to compete.

They looked like they would evolve into the first base ball powerhouse, but in the 1870s they continued their record of being pretty good but not great. Ultimately, this got them into franchise-ruining trouble, as the team refused to make a money-losing western swing in 1876, and with the center of the base ball universe having shifted to Chicago, they got kicked out of the league for it.

P - Frank Fleet - I don't know much other than the fact that he's a native New Yorker.
C - Dick Higham - SABR's biography project has an excellent bio of him. The son of a big cricket star of the 1850s, Higham was born in England, came to America as a child, and played for New York for most of the 1870s. His biggest claim to fame was being banned for life as an umpire in 1882 for allegedly throwing games.
1B - Joe Start - Start was a native New Yorker who was in mid-career by 1871. He was a base ball star even before the Civil War, and played for some of the great Atlantic club teams of the 1860s. He played in the major leagues until the mid-1880s and lived until 1927, dying at the age of 84.
2B - Charlie Smith - He only played in the big leagues in 1871, so little is known of him.
3B - Bob "Death To Flying Things" Ferguson - Like Joe Start, Ferguson was a veteran of the Atlantics who was in mid-career by 1871. He scored the winning run for the Atlantics in their historic victory over the Cincinnati Red Stockings. He was the player-manager of the 1871 Mutuals, and has been credited with being the first switch-hitter. (Certainly, managers started recognizing the platoon advantage in the 1870s.) After his career he became an umpire (a very common career path at the time), and umpired until the early 1890s. He died of apoplexy at age 49, and this obituary speculates that his death may have been brought on by too much smoking. (It's always interesting to find pre-20th century references to the dangers of smoking.)
SS - Dickey Pearce - Pearce was already 35 years old in 1871, and his base ball career was winding down. He and the ill-fated James Creighton (who died in 1862 just as he was becoming famous as the game's best pitcher) were the first two base ball superstars. Pearce actually created the modern shortstop position in the 1860s, as he realized most of the balls were hit to that area of the field and thus moved there for defensive purposes. He first joined the Atlantics in the mid-1850s, and was a star of the many champion teams of the 1860s. There is a phenomenal detailed bio of Pearce here - too much to say about a guy who was basically at the end of his career when professional base ball was taking off.
LF - John Hatfield - He was another star of the 1860s, although one with a more unsavory reputation. He played with the Cincinnati Red Stockings in 1868, the last season before professional players were expressly allowed, but he already had a reputation as a "revolving" player - one who would jump from team to team. It is almost certain that he was being paid somehow for his services, and when he amassed debts in Cincinnati he left for his old club in New York. According to his obituary, Hatfield also set a record in 1872 for throwing a base ball for long distance.
CF - Dave Eggler - He started with the Mutuals in 1868, and was a solid professional throughout the Association years and into the early 1880s. For such a solid, long-term veteran, there's not a lot of biographical material on him, although Wikipedia does offer the unsourced statement that he died in 1905 after being hit by a train.
RF - Tom Patterson - Even less is known about Patterson, who played throughout the Association era. From his ratings, he looks like a better fielder than hitter.

So for the most part, the Mutual club is hoping to contend in 1871 by using players who were stars of the 1860s. Not all of them are past their prime, but this could still spell trouble with strong teams in Boston and Philadelphia.