Each of the Premier League's 20 clubs have someone they probably cannot do without if objectives for the season are to be met.
For Liverpool, that's Adam Lallana. The sight of Lallana limping down the Wembley Stadium tunnel with a thigh injury was a sore one for Liverpool fans. The playmaker could miss five vital matches in their push for a top-four place.
To see who is crucial to other Premier League clubs' success, click here.