The England international was full of praise for his fellow centre back and says the young defender can continue to learn from the other defenders in the Toffees squad
England international Jagielka said that the Republic of Ireland under-21 international was among the team's best players when he made his Premier League debut in January against Tottenham Hostpur and that the new contract will help to 'settle him down'.
"Duffy's a great lad and he's going to be a good centre-back," Jagielka told evertonfc.com. "He obviously went out on loan and did really well and then we got a few injuries at the back and a few people weren't sure whether he'd be able to step up and handle it.
"But, fair play to him, I think he was up there amongst our best players in most of the games he played in."
Duffy has made just one appearance for the Goodison Park club this season, coming on as a substitute during the side's 5-1 Capital One Cup victory over Leyton Orient and Jagielka believes that he can continue to learn from the other defenders in the squad.
"It's nice for him to get a new contract and I think it will settle him down again. And the longer he stays around the squad hopefully learns from the rest of the defenders and the rest of the team.
"Hopefully that will turn him into a better player," concluded Jagielka.