Saints centre Andy Symons faces a scan on his knee injury on Monday.
The former Gloucester man was forced off at half-time in the 17-15 Gallagher Premiership defeat at Bath.
Symons was making his first start for Saints, but after trying to battle on, he had to be replaced.
Andrew Kellaway was the man introduced, making his Saints debut in difficult conditions at The Rec.
And Saints boss Chris Boyd said: "He (Symons) will require a scan on Monday. He's got a little problem with his knee so we won't know the extent of that until after the scan.
"It was tricky conditions for Andrew (Kellaway) and he didn't get a lot of opportunities but he'll be better for the game he's had."
Following their third defeat in four games this season, Boyd could look to mix things up for the trip to Bristol next Saturday.
"We'll put out the team we think is right against Bristol," he said.
"It's obviously a pretty important game for us. They're all important but we'll pick the best side we can next week.
"They (Bristol) have been going well and they play a lot of football.
"They've got some really good quality individuals and they're going to be a handful at Bristol."