Fill a cell with random values by drawing from certain cells in Google Sheets

I'm creating some scoreboards for tournaments.
After the initial phase, the fished-out players (below in red) access the elimination phase (SEMIFINALS) by placing themselves randomly in the scoreboard (below in the "?" cells in red), so I need to fill one or more cells randomly by "fishing" from previous cells.If a player goes to match #9, the other will have to go to #10. A player cannot go to both matches.How can I do it?

Tournament test