Different use of Apple Numbers database

This whole idea of listing the players each player has not played is going to be a hot mess until all players have played almost all other players. I have changed the formulas to match your more recent explanation but I am thinking you might be better off simply applying a conditional highlight (conditional cell fill color) to the cells that are 0 and then pan around to find who hasn't played who.

You can expand these tables. I kept them the same size as before.

Names are listed in Table 1 column A

Table 1::B1 =OFFSET($A$1,COLUMN()−1,0)

Fill right to complete the row

Table 2::B1 =Table 1::B1

Fill down to complete the column

Table 2::B2 =IF(AND(Table 1::B2≠"",Table 1::B2=0),Table 1::B$1,"")

Fill across and down to complete the columns and rows, except the last column

Last column is the same as before

K2 =TRIM(TEXTJOIN(" ",TRUE,B2:J2))

fill down to complete the column

Hide columns B:J

I moved everything up a row on the data table (Table 1). You left the header row blank and started in row 2 for some reason.

Formulas in Table 2 are

B2 =IF(AND(Table 1::B2≠"",Table 1::B2=0),Table 1::$A2&Table 1::B$1,"")

Fill down to the end of the table and across to column J

K2 =TRIM(TEXTJOIN(" ",TRUE,B2:J2))

Fill down to the end of the table.

One day if/when Apple fixes a bug in TEXTJOIN, TRIM will no longer be needed in this formula.

Hide columns B:J in Table 2.

If you don't want column A, delete it.