Ludlam sustained a thumb injury during the defeat at Saracens last time out, though he did manage to complete the full 80 minutes in that match.
Ribbans has not played since the European Challenge Cup defeat at Gloucester on April 16, while Augustus limped off inside 10 minutes against Harlequins on April 29.
And when asked about the trio's availability for this weekend's encounter, Boyd said: "I don't think any of them have ruled themselves in or out yet.
"Lewis has got through a bit of training and he could well come into consideration but it's not certain yet.
"David Ribbans is on his way back, but whether he's going to be ready for the weekend I'm not sure.
"Juarno Augustus is on his way back but whether he's going to make it I'm not sure.
"None of them have really ruled themselves out yet."
Saints will definitely be without Teimana Harrison and Conor Carey as both players have had surgery on knee injuries.
Tom Wood has been battling a shoulder injury since February and also looks likely to miss out this weekend.