MELBOURNE, AUSTRALIA - APRIL 29: Lance Franklin of the Swans looks dejected after a loss during the 2017 AFL round 06 match between the Carlton Blues and the Sydney Swans at the Melbourne Cricket Ground on April 29, 2017 in Melbourne, Australia. (Photo by Michael Willson/AFL Media/Getty Images)

The Sydney Swans have confirmed star forward Lance Franklin has suffered a serious hamstring injury at training on Wednesday.

Scans revealed he had avoided tendon damage, but the injury is believed to be worse than the left hamstring problem last year that sidelined him for nine weeks.

Swans head of football Charlie Gardiner said Franklin was set for a long stint on the sidelines.

"The medical team received the results earlier today, it confirms the injury, it confirms it's a pretty decent hamstring injury," Gardnier told sydneyswans.com.au.

"It's on his right side so he has no history of injury to that side, it's a new injury. We can't say right here and now how long he'll be out, but we know it's a decent injury and he won't run probably for the next three to four weeks.

"One of the positives is that there is no tendon damage to the hamstring.

"We think it's slightly worse than the injuries he sustained last year mid-season, and he missed about nine weeks. That might be an indication but we just won't know until he continues his rehabilitation and we see how he progresses."