I've located a photo of Seth Sigsby of the 1893 New York Giants. He came to the club from Union College in Schenectady. I've found two versions of the team photo, one from the 1893 Union College Yearbook and one from this antique store:
http://www.antiquesportsshop.com/baseballphotos.html
I emailed the store and they provided me with a list of players pictured. Unhelpfully, the list of players in the photo is not sorted by row.
I know it was customary for team photos of the era to have the team pitcher to be featured holding a baseball in the photo and for catchers to have their mitt and mask in view.
I've included a roster list from the 1893 Yearbook, which confirms that Sigsby was the club's sole pitcher. I believe he is seated next to the club's catcher C.A. Sullivan in the bottom row at the far left.
It's a bit speculative I will admit, but I think there is a reasonable case that it is Sigsby.