Chicago Bears linebacker Jon Bostic has been fined $21,000 (£13,500) after his hit on San Diego Chargers wide receiver Mike Willie was deemed to be illegal.

Bostic was not flagged during the play, in which he forced Willie to spill the ball while the receiver was collecting a short pass, resulting in the pass being ruled incomplete.

However, the 22-year-old rookie was fined for "lowering his head and making forcible contact with a defenceless player's body", and he admitted that he is still learning about all of the intricacies of NFL rules.

"I'm still trying to figure that stuff out. Obviously I'm new to the league. There's going to be a lot of new things I'm going to have to find out," ESPN quotes Bostic as saying.

"I'm learning from the older guys and really just finding out the process. I'm really just figuring out all of this stuff."

Bostic was selected as the 50th overall pick in this year's NFL Draft.