England coach Stuart Lancaster will be worrying over the fitness of injured Northampton duo Dylan Hartley and Courtney Lawes after both forwards sustained knee injuries in the Saints' 16-6 Premiership loss to Saracens at Franklin's Garden's.
Both were forced off the field before the start of the second half.
Northampton director of rugby Jim Mallinder did not reveal how serious the injuries were but both players will be assessed by England this week with the squad set to meet up on Sunday.
"They've done something, but we will know a lot more later," said Mallinder.
"I think Lawes and Hartley are the sort of characters that if they had just got a knock and they will be running around on Monday they wouldn't have come off.
"Courtney tried to carry on, but he was unable to do so. You want them on the field and getting through games. It was disappointing they had to go off."
Lawes was out for large parts of last season with an injury to his right knee. The England lock left the field in the 27th minute with a troublesome left knee.
And Hartley injured his knee just before the break and did not play during the second half.
He will be hoping they recover in time for next week's clash with Leicester at Welford Road along with Stephen Myler, who suffered a hamstring injury.
"Courtney and Dylan join up with England tomorrow and we will have to wait for a decision whether they are rested or not for Leicester," he said.
"Stuart will look to retain his starting 23 and I guess the others will be returned to their clubs.
"It doesn't help when you have two key England lads and Stephen Myler going off with injuries, but I thought in the first half we played pretty well into a big gale, we played some good rugby."