ST KILDA midfielder Zak Jones is in a race against time for round one after suffering his fifth hamstring injury in the space of two years.
Jones strained his left hamstring at training recently after also being forced out of a match simulation session in early February with a tight back.
The 25-year-old, who missed two games last year with separate hamstring setbacks, will sit out the Saints' two pre-season fixtures against North Melbourne (February 25) and Carlton (March 4).
And with just 33 days until the club's season-opener against Greater Western Sydney, Jones is in doubt after being listed as sidelined for a minimum of three weeks.
It comes after midfielder Dan Hannebery recently sat out of training for more than two weeks dealing with a calf complaint after a history of soft-tissue setbacks.
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Veteran signing James Frawley has also been managed on a modified program after being coaxed out of retirement by the Saints.
Meantime, second-year midfielder Ryan Byrnes will require surgery to repair a hamstring tendon injury he suffered at training last week.
The Saints anticipate Byrnes' recovery to take a minimum of eight weeks.
With recruit Brad Crouch to also miss the opening two matches of the season through suspension, the midfield door could open for ex-Tiger Jack Higgins and youngster Jack Bytel.