Speedster and national contracted player Tony Ensor has torn cartilage in his knee and is due to have some minor surgery in the next few days.
He injured his knee in the first game of last weekend's regional sevens tournament in Timaru and it was hoped it was only a minor injury.
But he is likely to take about four weeks to recover and is unlikely to be fully fit in time for the national tournament in Rotorua on January 17-18.
Otago sevens coach Luke Herden said it was disappointing for Ensor as he was looking sharp and had made some real progress in the past couple of months.
He may still accompany the team to Rotorua and assist in some way.
Kieran Moffat, a senior player for Otago at the past two national tournaments, will also be absent.
Moffat (25) is going overseas with his partner for an extended period. He will also be available for Taieri and Otago next year.
Moffat, a midfield back and wing, who played in the forwards for Otago in sevens, played a dozen games for Otago.
He has not signed for any club overseas.
Herden said Moffat's experience would be missed.
Herden has called in Harbour loose forward Naulia Dawai into his squad and he should add some bulk and size in the forwards.
The side has drawn Auckland, Manawatu and Mid Canterbury in its pool at the national tournament so there will be no easy games, Herden said. The draw for the games has not yet been made.
Otago sevens players have the next couple of weeks off, though will still train on individual programmes. They come back together on January 6 in Dunedin.
