Jetta has been missing since round 10 with bone bruising in his shin, and coach John Longmire says he is at least a fortnight away from being able to run and five weeks away from playing.
With just seven matches remaining before the finals, that leaves the 24-year-old flyer in the same boat as a number of teammates battling to get back in the team for the run home.
Sam Reid is expected to sit out another five to seven weeks with his torn quad, while Adam Goodes is another month away following knee surgery and Lewis Roberts-Thomson (knee) may not play again this year.
“Lewis Jetta probably is still two weeks away at the moment from running," Longmire told the club's website.
"So that will take another two or three weeks from that point to get back into training and playing, and we’d expect that he is still another five weeks away.
“We understand with the type of injury and the bone bruising that it is that it can turn nasty if we don’t look after it, so our priority is to look after it.
“As frustrating as it is for everyone … hopefully we’ll start him running and training after that.”
There has at least been some good news for the premiers, with Rhyce Shaw finally available after his long battle with an abdominal tear.
Shaw has been out of the side since round two, but will make his return through the reserves against Gold Coast this weekend if he passes a fitness test.
Roberts-Thomson remains in the 'indefinite' category, however, with his knee injury, with Alex Johnson (knee) and Tommy Walsh (hamstring) already ruled out for the season.
Ben McGlynn also picked up a hamstring injury against Greater Western Sydney on Sunday, although that has been offset by his three-week suspension for striking.
Both Jetta and Shaw were initially only expected to miss one or two weeks and Longmire admits the situation has been frustrating for all involved.
“It’s been a bit disappointing and a bit frustrating I guess for everyone with a few of those longer-term injuries that we’ve had,” he said.
“They have been a bit disappointing when we expected them back a little bit quicker … but unfortunately that’s what happens sometimes.
“It’s disappointing but hopefully they’ve still got a chance of playing and contributing for us in 2013.”
The Swans have coped with their injury toll remarkably well, still sitting in the top four ahead of this week's trip to Perth to face West Coast.
The injuries mean some fringe Swans such as Brandon Jack, Jed Lamb, Jesse White and Andrejs Everitt can now expect some more game time in the seniors.
Gary Rohan also made a welcome return from injury in the reserves on Sunday, and will enjoy some increased game time in the seconds this week.
"Hopefully there is some light at the end of the tunnel with Rhyce Shaw getting back this week and Gary Rohan already playing,” Longmire said.
“Rhyce at this stage, if he gets through the rest of the week training, we expect him to play some game time in our reserves, which is fantastic.
“Obviously Gary on the weekend came back and his game time will increase.
“He looked fantastic last week."
James Dampney is a reporter for AFL Media. Follow him on Twitter @AFL_JD
