Toby Flood could be sidelined for several weeks after he suffered a knee injury during Leicester's defeat at Northampton Saints.
The fly-half limped off just before half-time as the Tigers lost 27-19 at Franklin's Gardens.
"He's had a bang on his medial (knee ligaments)," Leicester Tigers coach Richard Cockerill told the Leicester Mercury. "We're assessing that now and he'll be seen by the specialists over the next 48 hours.
"It doesn't look ideal but we'll have to see. Let's not get carried away."
Flood missed a large part of last season with a ruptured Achilles.
Northampton director of rugby Jim Mallinder felt Sunday's opening Premiership win over Leicester was a superb all-round display.
The Saints were looking for a confidence-boosting win over the reigning champions to get their season up-and-running and they edged out their East Midlands rivals 27-19 at Franklin's Gardens.
Prop Soana Tonga'uiha got the ball rolling with two tries within the first five minutes of the game to give the home crowd something to cheer about, with Stephen Myler converting both.
Myler landed another three-pointer before the break but Alesana Tuilagi crossed the whitewash to leave the Tigers trailing 17-7 at half-time.
Brian Mujati touched down in the second period for Northampton with Myler again adding the extras and, with Shane Geraghty also landing a penalty, the hosts looked home and dry.
But Leicester are champions for a reason and they came roaring back with two tries from Scott Hamilton, but it was too little too late and the points went to the home side.
Mallinder was delighted with he result and the performance and felt that there were excellent performances all over the park.
"It was a combination of forwards and backs working together," he told the BBC. "It gives us all sorts of options. I thought the props played well. The pack was really good. The pressure was on us as it was a home game.
"We started well, Leicester came back as we knew they would but it was really pleasing to come out with a 'W'."