Saints went down 32-24 to the Black and Whites and Walsh was forced from the field after just two minutes.
The club will assess him in the next few days but coach Keiron Cunningham suggested he won’t be available for “a few weeks”.
Cunningham prasied his players following the close defeat.
“My players were outstanding and were hard done to,” he said after the match.
“They should have got more from the game. The level of effort went through the roof. Hull are on the crest of a wave and we just fell a little bit short in certain areas.
“But we lost Walsh in the first minute and the penalties were 10-2 in the first half. If anyone says they were eight penalties cleaner than us, I’ll call them a liar.
“We couldn’t build any pressure. It’s frustrating for me as coach but I feel for the players because they don’t get any reward for their efforts.
“We definitely deserved something out of the game. It’s a bitter pill to swallow. I’d told my players they should be proud.
“We fought really hard for each other. If we can bring that fight and resilience every week, we’re not going to be far short.”