Bulldogs general manager of football Phil Gould confirmed to AAP that Sexton had a "badly bruised clavicular joint" and would have a scan on Monday to "rule out a fracture".
Gould said via text that Crichton had sustained "a low- to moderate-grade syndesmosis" injury in the 26-18 loss to Melbourne on Friday night and would probably miss "two to four weeks".
The star centre will not require surgery, keeping him in the frame for a possible return if the Bulldogs make the grand final.
Gould revealed Crichton also suffered a strain of his first tarsometatarsal joint in the foot, but crucially avoided a Lisfanc injury that would have ruled him out for longer.
In a further blow to the Bulldogs, fellow centre Enari Tuala is out of the finals after he suffered a fractured tibia against the Storm, Gould confirmed.
But there is better news on star back-rower Viliame Kikau, who also left the field in the first half against the Storm after copping a stray elbow, before passing an HIA.
There was a concern for an eye-socket injury, and his face was swollen when he returned from Sydney on Saturday morning.
Gould confirmed it was a suspected eye-socket fracture, but that it "appears to be stable".
"He probably fractured it the previous week against the Sharks," Gould said.
"That's why it hurt so much when he got a knock early in the game against Storm.
"(There is) no concussion, just pain."
But it is Sexton's injury that could create more headaches for the Bulldogs.
The playmaker soldiered on through the final 35 minutes after he was hurt attempting to tackle a runaway Will Warbrick early in the second half.
Recalled to the Bulldogs side for the first time since mid-July, Sexton came off the bench and scored a try with his first touch and had a solid game.
Canterbury could consider starting Sexton, if fit, in the halves and shift Matt Burton to centre against the Panthers to cover their backline crisis.
The Bulldogs will get centre Bronson Xerri back from concussion in a major boost. Winger Marcelo Montoya (ankle) is also a chance to return after missing the Storm loss.
Regardless, they now face a tough task against four-time defending premiers Penrith in front of what could be close to a record crowd at Accor Stadium.
The two sides played out one of the best games of the season in round 17, with a Nathan Cleary charge-down the difference in Penrith's 8-6 win at CommBank Stadium.
That result lifted Penrith back into the top eight after sitting last on the ladder as recently as round 12, with the Panthers having seemed finals-bound and in pursuit of a fifth straight title ever since.
