Speaking to the playing group, senior coach Brett Ratten confirmed the news that the pair of exciting additions will feature in the Saints' season opener.
Hayes joined the St Kilda earlier this year through the Supplemental Selection Period, having enjoyed a career-best campaign with Woodville-West Torrens in the SANFL.
The 25-year-old averaged 19.7 disposals, 7.7 marks, 4.4 tackles, 2.4 clearances and over a goal per game last year on his way to premiership success with the Eagles, with Hayes also earning best-afield honours in his side's grand final victory.
The versatile tall is capable of playing in the ruck, as a forward target and behind the ball, offering Ratten flexibility across his magnets board.
Owens, who was taken with Pick 33 in last year's National Draft, joined the Saints after impressing throughout his time with the Sandringham Dragons, Vic Metro and St Kilda's Next Generation Academy.
Standing at 191cm, Owens is a tall, bullish onballer who is sure to have an instant impact at AFL level.
The talented teenager is sure to contend for minutes in St Kilda's engine room, while also likely to rotate forward.
The Saints will announce their 22-man side at 6:20pm on Thursday, just over 24 hours prior to their Round 1 bout with Collingwood at Marvel Stadium.