You could use the query module to select the entry IDs of all entries in that channel that are not in the playa and pass the IDs to the channel entries tag. Here's an (untested) example.
{exp:channel:entries dynamic="no" entry_id="{exp:query backspace='1'
sql='SELECT entry_id FROM `exp_channel_titles`
WHERE channel_id = 6 AND entry_id NOT IN
(SELECT `child_entry_id` FROM `exp_playa_relationships`
WHERE parent_entry_id=20229 AND parent_field_id = 28)'}{entry_id}|{/exp:query}"}
{title}...
{/exp:channel:entries}
You will need to replace the channel_id (currently 6) with your channel id, the parent_field_id (currently 28) with the field ID of the playa field and the parent_entry_id (currently 20229) with the ID of the entry that has the playa field on it.