Jim Mallinder has confirmed Brian Mujati suffered a calf injury in Saints’ 17-16 defeat to Saracens on Sunday.
But the director of rugby is unsure how long the problem will keep his Springbok prop out for.
Mujati limped off in the 36th minute of the clash at stadium:mk, to be replaced by Paul Doran-Jones.
And the 28-year-old, who is set to leave Saints for French club Racing Metro next summer, could now be set for a spell on the sidelines.
“Not too sure,” replied Mallinder, when questioned about the severity of Mujati’s injury.
“He injured his calf so I’m not exactly sure what the extent of the damage is. Hopefully it’s not too bad.”
Meanwhile, Mallinder said after the defeat to Saracens that he agreed with Stephen Myler’s decision to take on a late penalty kick, which the fly-half missed.
Myler’s mammoth penalty attempt from inside his own half rebounded off the crossbar after the clock had gone dead, to leave Sarries celebrating the narrowest of wins.
And Mallinder said: “To be honest, I didn’t think he could have got it. I was definitely wondering but you’ve got to leave it to the player.
“He knows whether he’s got a realistic chance of kicking it or not. They’re the ones who are playing.
“I left it up to him and I think he probably did make the right decision to go for it.”