Arsene Wenger 's decision to leave alexis Sanchez on the bench backfired as first half goals from roberto Firmino .
Arsene Wenger 's decision to leave alexis Sanchez on the bench sadio Mane set Liverpool on course for a vital 3 - 1 win over Arsenal on saturday .
Arsene Wenger 's decision to leave alexis Sanchez on the bench backfired as first half goals from roberto Firmino and sadio Mane set Liverpool on course for a vital 3 - 1 win over Arsenal on saturday .