Swans ruckman Kurt Tippett has undergone scans after leaving the ground injured in yesterday's game against GWS.
The scans have confirmed that Tippett suffered a tear in one of his hamstring tendons that join his knee.
The initial prognosis is that Tippett will miss up to six weeks.
Young gun Harry Marsh suffered a hamstring strain in the same match and has been ruled out of Sydney's Round 13 clash with Melbourne.
But the news is better for speedster Gary Rohan who has been cleared of any hamstring damage as a result of bleeding near his hamstring from multiple corks.
Rohan will be tested later in the week but is expected to play.
Meanwhile Sam Reid suffered a calf strain at the beginning of the fourth quarter in the Swans NEAFL game at Spotless Stadium.
Reid will need to recover prior to running again and at this stage will be unavailable for three weeks.