Western Australia coach Adam Voges says it was a tough call to overlook Nathan Coulter-Nile and AJ Tye for contracts, but it needed to be done for team balance.
Coulter-Nile was told earlier this year that he wouldn't receive a contract renewal after he decided to focus his attention on white-ball cricket.
The 32-year-old, who plays for Melbourne Stars in the BBL, is set to explore the market in a bid to play 50-over cricket with a different state.
Coulter-Nile hasn't played a Sheffield Shield match since 2017 due to a series of injuries, while Tye hasn't played the longer format since February 2018.
Tye, who has played 26 T20s and seven ODIs for Australia, has continued training with WA and remains a chance of earning a contract upgrade later this year.
Paceman Simon Mackin and Matthew Spoors were others to miss out on a WA contract.
"That was a really tough decision for all the guys that we released," Voges said.
"Nathan's had a huge contribution in WA cricket. You look at our passes successes in white-ball cricket ... and Nathan's in every one of those photos.
"To leave him out, to leave AJ Tye out of our contract list - they were really tough calls. But we've got one eye on having a really balanced squad that's able to compete in all forms."
Paceman Cameron Gannon has been lured to the Warriors on a three-year deal to help bolster the bowling stocks.
The 31-year-old snared a Shield-high 38 wickets at an average of 20.92 last season - five more scalps than the competitions next best bowler.
Spinner Liam O'Connor has been upgraded to the senior contract list.
Voges expects left-arm paceman Jason Behrendorff (back surgery) to be fit for the start of the domestic season.
Behrendorff will initially be limited to white-ball cricket, with the hope he can return to Shield action near the end of the summer.
Jhye Richardson (shoulder surgery) has targeted a BBL return in December.
All-rounder Cameron Green, who played solely as a batsman last season, has recovered well from his back stress fractures.
The 21-year-old has tweaked his bowling technique in the hope of avoiding more back injuries.
The WA women's side has welcomed experienced Victorian right-arm leg-spinner Alana King, while fast bowler Zoe Britcliffe and Georgia Wyllie have earned upgrades to the senior list.
WA were dealt a blow when Heather Graham made the switch to Tasmania, while Sophie Devine (international duties), Kath Hempenstall and Ashlee King are others to leave.