Tevita Pangai Junior's return timeline has been reset to 'indefinite' by the Canterbury Bulldogs.

He will be joined on the sideline by Fa'amanu Brown, who suffered an elbow injury last weekend against the Warriors.

Missing the start of the season with a calf strain, Pangai Junior's return was originally set down for around Round 4, but it was revealed last week that he was yet to return to running.

Despite that, the Bulldogs at the time, still had his return set for Round 5 in official club communications.

In a new communication released on Tuesday, his return date has been set to 'indefinite' thanks to the calf strain. The club stated he was being monitored.

"Tevita Pangai Junior suffered a calf strain during a field training session," the club wrote.

"His progression continues to be monitored by Club medical staff."

That means the mystery injury rules the star forward out of at least the first five weeks of the season, with the Bulldogs playing through a lack of forward depth.

They have won two out of their first four, but suffered a disappointing loss to the New Zealand Warriors in Auckland last Sunday, and now prepare for an exceptionally difficult period ahead, with the North Queensland Cowboys, South Sydney Rabbitohs, Parramatta Eels and Cronulla Sharks their next four opponents.

Also added to the Bulldogs' casualty ward is Fa'amanu Brown.

He failed to complete the game against the Warriors after playing from the bench, and the club have now confirmed he has dislocated his elbow.

"Fa'amanu Brown suffered a left elbow injury during the Round 5 match against the New Zealand Warriors," the club wrote.

"His elbow was relocated in hospital and he has now returned to Sydney where he will require scans and a specialist review. Management for his elbow will be guided by specialist advice."

His return date, like that of Pangai Junior, is indefinite.