North football director Geoff Walsh told NMFC.com.au that Tarrant had been diagnosed with a tibial stress reaction that would sideline him for the first few rounds of the season.
"Unfortunately, we know from what we experienced with Robbie last year that we're dealing with a similar situation," Walsh said on Thursday afternoon.
"However, it's nowhere near as severe this time around and thankfully our medical team has identified the symptoms early, allowing us to take a very proactive approach with his training and treatment.
"Like last year, we will be very cautious and won't be playing Robbie until he is fully fit and ready."
Click here to read the full injury list for all clubs
Walsh said Tarrant's leg injury had resurfaced despite the key forward being put on a heavily modified training program this pre-season.
Tarrant's problems began early last year and, after struggling through the first three rounds, North opted to rest him.
The Roos were initially hopeful Tarrant would spend only a short time on the sidelines, but his injury flared whenever he tried to increase his training intensity.
Tarrant returned to play North's final 10 games of 2013, but struggled to train between games.
Tarrant's injury increases the likelihood that Majak Daw will be part of the Roos' round one team against Essendon.
The Sudanese-born forward replaced Tarrant in the Roos' team in round four last season, playing six games before being dropped to the VFL.
Twitter: @AFL_Nick
