Aleksander Barkov, Brandon Montour and Jonathan Huberdeau scored, and Knight made 26 saves for the Panthers (17-4-4), who had won three in a row.
"I feel like we had some chances," Montour said. "Obviously, [Husso] played a good game. I feel like we had a couple right in front of the net where we might score usually, but it is what it is. Something happens like that, you can't score every time. The guys battled hard, and we got one point out of that."
Saad gave the Blues a 3-2 lead at 6:48 of the third period, deflecting a one-timer from Ivan Barbashev at the top of the crease four seconds after a power play expired.
"I was kind of just in the area, have your stick in the right place," Saad said. "It just deflected off me and went in. Obviously, it was great movement there on the power play finishing it off. Sometimes you've got to be lucky out there."