The setback adds to a dramatic 12 months for the South Australian, who gained a chance in the AFL with St Kilda after impressing as a train and trial player through the pre-season before tearing his ACL in Round 6 against GWS.
The 26-year-old is now expected to miss a further 8-10 weeks after suffering a foot injury at training, requiring surgery after scans discovered a crack in a metatarsal in Hayes' left foot.
“Jack has been dealt a really rough hand since debuting last season,” St Kilda Performance, Medical and Operations Manager David Misson said in a club statement.
“Jack had just returned to full training after completing his ACL rehabilitation, so for this to happen is very disappointing.
“The recovery period for an injury like this is typically between 8 to 10 weeks.
“His resilience has been unfairly tested for an athlete so early in his career, but we know that he will attack his rehab in the same professional manner we have become accustomed to.”
Hayes had only returned to full training in recent weeks, being among a handful of key Saints players returning from injury as they prepare for a new season under returning coach Ross Lyon.
The injury isn't the first major setback for the Saints this pre-season, with fellow tall forward Max King sidelined for at least the opening month of the season after requiring shoulder surgery.
With St Kilda's Round 1 bout against Fremantle just two months away, Lyon could be tasked with naming a side without both Hayes and King.
The remainder of St Kilda's list is beginning to look healthier, however draftee Olli Hotton will miss the first half of his debut campaign after sustaining a stress fracture in his back in the pre-season.
Defender Nick Coffield, who is also returning from an ACL injury sustained last year, suffered a hamstring injury that has delayed his return, however is expected to be available for Round 1.
St Kilda will host Fremantle at Marvel Stadium on Sunday, March 19 to begin their 2023 season.