Niemi joined Fulham from Southampton for �1m in January

The 34-year-old Finnish international was replaced by Czech Republic shot-stopper Jan Lastuvka in Saturday's 2-0 defeat by Blackburn.

Cottagers boss Chris Coleman said: "Antti had a little bit of cartilage floating around and should be back in three weeks to a month."

Lastuvka, 24, is on loan at Craven Cottage from Shakhtar Donetsk.

He was making his first Premiership appearance at Ewood Park and conceded a goal within six minutes when he was beaten by Shabani Nonda's speculative strike.

Benni McCarthy also scored before half-time but Lastuvka grew in confidence as the game went on and made two good saves from Brett Emerton and Lucas Neill.

Coleman said: "It was difficult for him to come in today and obviously he was nervous but overall I thought he was okay."