SYDNEY veteran Nick Smith's already frustrating season could in doubt before it began after he was forced to have a second operation on his troublesome hamstring on Tuesday.

Smith injured his hamstring tendon against Melbourne at the MCG in round 21 last year, and while the Swans were hopeful at the time the issue would heal naturally, he eventually had surgery to fix the issue. 

FULL FIXTURE Every round, every game

The 30-year-old had built up his training over the pre-season and was running in straight lines early this year, but the All Australian hasn't been able to push himself any further to get himself back on the track. 

Sydney football manager Charlie Gardiner told that the Swans' medical staff sent Smith for another operation on Tuesday to help fast-track his recovery. 

WHO MAKES FINALS? Do the 2019 Ladder Predictor

"Nick worked hard to get his injury right over summer and earlier this year but unfortunately hasn't been able to get back to full training," he said. 

"A decision was made earlier this week to undergo some more surgery on that hamstring to try and relieve some of the scar tissue around that hamstring.

"Hopefully that surgery will put his issues behind him and we can see him back on the park soon."

Smith's absence has robbed the Swans' backline of its most reliable lockdown small defender, and with Jarrad McVeigh (quad) and Heath Grundy (back) also missing, their experience has been a massive loss. 

One of Sydney's most consistent and durable players over the past decade, Smith becomes a restricted free agent at the end of this season.