The Knights held their first session since the Christmas-New Year break on Thursday morning, but a large number of high-profile players were conspicuous in their absence.

The Newcastle Herald revealed on Monday that the club had been blindsided by an outbreak of COVID-19.

Knights officials have declined to divulge how many players have contracted the coronavirus, but it is understood to be in double figures.

The Herald observed Thursday's conditioning session and counted fewer than 20 players on the field.

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A full NRL squad should comprise at least 36 players.

A host of other NRL clubs are facing a similar dilemma.

Players who have tested positive have been ordered to isolate at home for a mandatory period.

Their teammates will be required to undergo rapid antigen testing before each training session, possibly for the entire season ahead.

The Knights were forced to break for Christmas ahead of schedule, on December 16, after a young player and club employee tested positive.

Given the extended lay-off, and limitations imposed on the players in isolation, Knights coach Adam O'Brien and new physical-performance manager Hayden Knowles face a logistical challenge to whip players into shape for the club's first pre-season trial, against Canterbury on February 21.

Thursday's training resumption kicked off with a heavy conditioning session as O'Brien cast a close eye over his troops.

Among those in attendance was star signing Dane Gagai, who has returned to Newcastle after four seasons with South Sydney.

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