Thanks @Reaser!
I was actually able to trace back games involving key Pittsburgh players and teams two more seasons. In ’88, 500 showed up at Recreation Park to watch a game between Pittsburg and Allegheny, but the teams were short on players! They ended up playing 9 v. 9. They played a scoreless 45 minutes, took a 15 minute break and after the break, Allegheny finally scored the winning TD for a 4-0 final. The
Post did not reveal who scored but noted “the feature of the game was the playing of Messrs
Carnegie and
Thompson, of the Allegheny representatives.”
One season prior, in 1887, The
Post published this game announcement:

- 1887-1.png (135.7 KiB) Viewed 2475 times
But, bad weather played a factor again. In fact, most of the major papers simply reported football had been rained out, but the
Commercial Gazette on the back page (with pigeon shooting) actually reported on the game under the headline "ONLY A SCRUB GAME" (The Harvard/Yale game was front page news that day). Again, there was a player shortage for the big game. This time, instead of playing with less than 11, Allegheny just borrowed players from Pittsburg:


- 1887-2.png (80.75 KiB) Viewed 2475 times
The game was played at Recreation Park and the reported final was 16-10.
Notice above, one of the Allegheny players to show up was not mentioned in
The Post's announcement - O.D. Thompson. This was 5 seasons before he hired Heffelfinger.
Another interesting thing is the presence of a Carnegie in '88. I don’t know who this was, but Andrew’s brother Thomas had 9 children including some sons who would have been the right age to play football at this time.