England and Northampton Saints lock Courtney Lawes is facing a late call on whether he will be passed fit to face the Ospreys.
Lawes left Franklin's Gardens after last week's 23-9 win over Harlequins in a special boot on his right foot.
With the 24-year-old now being assessed on a daily basis, Northampton forwards coach Dorian West revealed that a call on Lawes' fitness would not be made until closer to Sunday.
"Courtney picked up a little knock," West told the Northampton Chronicle and Echo.
"I don't think it's anything too serious but it's one we'll have to keep monitoring and we'll see where he is nearer the matchday."
West did also reveal that backs Ken Pisi and James Wilson could be in contention to return.
"They're both progressing and we'll see where they are at the end of the week, then decide which players are going to take the field," added West.
"The sort of injury James has had (a calf problem) takes a while but once you get up to speed it all happens quite quickly.
"We're hopeful he'll be available before not too long."
Northampton are currently second in Pool 1, four points behind Leinster.