"[Anton] Blidh is out [with an upper-body injury suffered in Buffalo], so I believe Studs will come up, need to confirm that later today," said Cassidy.
"At the end of the day, he's the guy who left [camp] the most deserving, so if that's the route we are going to go he's certainly the guy we are going to go to," said Cassidy.
Nick Foligno (upper-body) was also ruled out for Sunday's tilt and Craig Smith has been listed as questionable.
"Smith wasn't 100 percent throughout the game [in Buffalo]," said Cassidy. "I just felt like he was a little bit off; he's dealing with a nagging injury that we are trying to work through."
After a stellar 35-save outing in his Bruins debut on Friday night, Ullmark will get the call in net once again against the Sharks, who enter the contest - the first meeting between the two teams since Oct. 29, 2019 - with a 4-0-0 record to start the season.
"He deffinelty earned it, he was excellect [Friday] night. He deserves to go back in so he will go back in," said Cassidy