Duffy (21) has made just three appearances for Everton this season, most recently as a sub against Oldham in the FA Cup, but he could be pressed into action for next week's FA Cup quarter-final meeting with Wigan.
Jagielka needed surgery after a clash with Adam Le Fondre just minutes into Everton's win over Reading on Saturday and the England man could be out for some time – and that could open the door for Duffy. "He is going to get surgery on his ankle – not to repair the bone but to stitch it up. It's a bad, bad gash, it could be a couple of weeks and it's a real, real blow to us," said manager David Moyes.
"I'm not happy with the challenge that we've had on our goalkeeper in the last game that puts him out, and then I'm not happy with the challenge that puts Phil Jagielka out of the game.
"I don't mind robust challenges – I'm quite happy for a bit of that. But one that puts out arguably one of my best players, I'm not happy with that."