Everton goalkeeper Tim Howard will miss the next five to six weeks with a calf injury, manager Roberto Martinez has said.

The American missed Sunday's loss at Newcastle with the injury suffered against Stoke on Boxing Day, and is now set to miss out until well into 2015.

"Tim Howard will be out between five and six weeks with a calf injury," Martinez said at his press conference ahead of the New Year's Day game against Hull.

Joel Robles, who was with Martinez at Wigan, is deputizing and, while the Toffees boss is happy with him, he may look to bring in another stopper.

"I thought Joel was very calm against Stoke and did well against Newcastle. But we will assess whether we need cover," the Spaniard added.

Martinez said Howard's injury was unusual and admitted that it was a big blow to lose a player of his experience.

"He's picked up a calf injury in his left calf and that's something that as a goalkeeper is really unusual. It happened just kicking the ball against Stoke.

"Tim is going to be a huge miss, not just on the pitch but being around the place and having the calmness that he gives to the younger players and the know how that he brings to the dressing room.

"Tim is a big game player. When he plays for the national team in tournaments and when he plays for us he's used to that scrutiny and responsibility and he just embraces it.

"That's something that we need to have spread out throughout the squad. We need that big game, big team mentality and (to) cope with the expectations and whatever surrounds the performance."