LIVERPOOL -- Everton goalkeeper Tim Howard will be out for five to six weeks after suffering a calf injury, manager Roberto Martinez says.
And the Toffees boss will consider signing a keeper in the January transfer window in order to provide cover for the U.S. international's absence.
Howard, 35, suffered the injury while kicking a clearance during the 1-0 Premier League defeat at home to Stoke on Boxing Day.
Former Atletico Madrid and Wigan keeper Joel Robles, 24, has stepped in as a replacement, but Martinez has acknowledged that he now needs more cover in that position, with Howard not expected to play again until February.
The manager said: "That's an area in which we're a little bit weak at the moment, and we need to get stronger. Tim Howard is going to be out for between five and six weeks.
"He's picked up an injury to his left calf, and that's something that's really unusual for a goalkeeper. It happened just kicking the ball against Stoke at home."
Former Spain under-21 international Joel, who came on as a substitute for Howard against Stoke, then played in Sunday's 3-2 defeat at Newcastle -- only his second Premier League start since arriving at Everton in July 2013.
Former youth-team goalkeeper Russell Griffiths was named on the bench at Newcastle for only the second time in his career.
But neither Griffiths nor fellow 18-year-old Jindrich Stanek, a Czech Republic under-19 international signed from Sparta Prague last January, have ever made a senior appearance at club level.
For that reason, Martinez is considering whether to bring in back-up.
The manager said: "I think it's something we're going to assess. Obviously, Joel had his first start in the league this season at Newcastle.
"I thought he was really calm against Stoke in the second half, and against Newcastle, it was a great way of having that introduction.
"It's something we need to assess. We've just found out about Tim. We weren't sure how long he was going to be out for, but we have to make a decision, because we only have Russell Griffiths and Jindrich Stanek as the two young goalkeepers who have been working with the first team.
"So we need to assess that over the next few days."
Martinez believes that Howard's injury is a huge blow to Everton -- as much because of his dressing-room personality as his goalkeeping ability.
He said: "I think Tim is a big-game player. When he plays for the national team in big tournaments, and when he plays for us, he's used to having that scrutiny and responsibility. He embraces it.
"That's something we need to have spread out throughout the squad. We need to have that big-club mentality. To cope with the expectations, you need to be able to cope with whatever surrounds the performance and you need to be able to play well.
"Tim is going to be a huge miss -- not just on the pitch, but being around the place and the effect of calmness that he gives to the younger players, and that knowhow he brings to the dressing room.
"I would love to try to find a positive about him being injured, but I'm struggling."