Kelly signed a new deal with the Reds in February 2013 - now he aims to reward the commitment from Rodgers and the club with performances out on the pitch.
"We had been talking about a new contract before I got injured," the defender told the Liverpool Echo.
"I only had 18 months to go so it was great to get that sorted and be able to focus solely on getting fit.
"After starting last season well I think I showed Brendan what I could do. I need to repay the manager by trying my hardest and keeping fit throughout the next four years."