England coach Stuart Lancaster will be fretting over Northampton duo Dylan Hartley and Courtney Lawes after both suffered knee injuries in the Saints' 16-6 Aviva Premiership defeat to Saracens.
Northampton director of rugby Jim Mallinder did not reveal the full extent of their problems, which forced both off before the start of the second half, but they 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," Mallinder said. "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."
He added:"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."
Mallinder will be hoping the pair recover for next week's east midlands derby against Leicester at Welford Road along with Stephen Myler, who suffered a hamstring injury and came off with Lawes.
"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."
Saracens defence and forwards coach Paul Gustard was delighted with his side's performance as they inflicted a first home defeat of the season on Saints.
"We pride ourselves on the defence," said Gustard. "It is an easy way to demonstrate the unity of the squad. When things get tough we can rely on having a friend to the left and to the right to fight for each other and get that turnover when we need it.
"The scramble defence from Charlie Hodgson, somebody who was vilified while he was at Sale for not being a good defender, I think he has come to Saracens to show what a good player he is and what a good defender he is."