Posted By: 
robIt is definitely the 1891 Boston team as it is written in period ink on the bottom of the picture.  I'll put question marks where I am uncertain and leave the question marks off where I feel strongly about the ID.  The Boston team starting back row, left to right:  Charlie Buffington, Paul Radford?, Hugh Duffy, John Irwin?.  Middle row:  Tom Brown?, George Haddock?, Morgan Murphy?, Arthur Irwin, Duke Ferrell, Dan Brouthers.  Bottom row:  Bill Daley, Cub Stricker and Darby O'Brien.  
For the New York photo I am much less certain.  My guesses starting with the back row left to right:  Stump Weidman, Mike Slattery? or Mike Tiernan?, Jim Mutrie (in top hat), Mickey Welch? or Mike Slattery?, Tim Keefe?.  Front row:  Canonball Titcomb? or Mickey Welch?, Elmer Cleveland?, Elmer Foster, George Gore? and Cannonball Crane.  For this photo I am uncertain of the year but the uniforms fit for 1887 and Mutrie's time as manager narrows it down to that period also.