Has there ever been a 9–1 in the Liga MX?

Yes, 1 time.

The only time: May 4, 1947, León beat Marte (León 9–1 Marte).

Nearby scores

1. 10–0 Never
2. 10–1 2 times
3. 10–2 1 time
4. 9–0 2 times
5. 9–1 1 time
6. 9–2 6 times
7. 8–0 7 times
8. 8–1 5 times
9. 8–2 11 times