Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How many different partners played in the finale in 1973?

### Inputs:
table_name: table, columns: ['Outcome', 'Year', 'Championship', 'Surface', 'Partner', 'Opponents in the final', 'Score in the final']

### Response:
SELECT COUNT Partner FROM table WHERE Year = 1973