Riki Flutey's participation in England's opening autumn international against New Zealand is in doubt.
Flutey limped off with a calf injury half an hour into Wasps' 37-10 Aviva Premiership defeat by Northampton at Adams Park yesterday.
The 30-year-old, a near-certainty to by selected at inside centre by Martin Johnson next month, is being assessed by England's medical team.
A clearer picture over his availability for the All Blacks' visit to Twickenham in two weeks should emerge over the next 24 hours.
"Riki's pretty sore at the moment. It's an injury to the calf, quite high," said Wasps director of rugby Tony Hanks.
"He's being assessed by England. Hopefully he won't be out for too long.
"These things can take a day or two before you learn how bad they are, but he was definitely pretty sore."
England have three other options in their elite player squad for the number 12 jersey in Shontayne Hape, Jonny Wilkinson and Toby Flood.
Hape filled the position during the summer tour to Australia and New Zealand but lacks Flutey's experience, while neither Wilkinson nor Flood are specialist inside centres.
England are assessing the fitness of two further Wasps players with lock Simon Shaw and scrum-half Joe Simpson suffering from calf and shoulder problems.
Shaw was withdrawn from the Wasps line-up on Friday after sustaining the injury, giving Saints the confidence to overwhelm their opponents up-front.
Tongan prop Soane Tonga'uiha helped himself to two tries, while Stephen Myler, Chris Ashton and Courtney Lawes also crossed as Saints climbed to second place in the table.
Three of the tries came from line-out catch and drives that saw the Wasps pack take an embarrassing hiding.
Director of rugby Jim Mallinder admitted that Saints scented blood as soon as they discovered Shaw had been ruled out.
"That was a very satisfying performance. We've never won down here before so we knew we needed to play well and we certainly did that," he said.
"We looked at their team sheet and thought we have a really good chance of strangling them up-front.
"Simon was a massive loss to them as he's particularly good at stopping the driving maul.
"He's got massive experience and is a massive bloke. To see he wasn't playing was a boost."