And Saints director of rugby Jim Mallinder confirmed his absence for the Leinster clash although there was better news from winger Chris Ashton who has been given a clean bill of health after being on the receiving end from Manu Tuilagi.
Mallinder said: "Tom is out. He trained yesterday with the team but it's one week too soon. He is not 100 per cent fit.
"He's very, very close and I guess if we were a desperate team we could have taken the chance with him.
"But it's not worth it. We have a strong squad who have been playing well and unfortunately he won't be running out on Saturday.
"It's a big blow but when you get to this stage of the season with only one player out, then you'd probably take it.
"Chris is fine. He took a heavy blow. He wasn't concussed or knocked out and carried on playing.
"He's sat out contact training - he'd already got a split above one eye before that incident.
"The doctor was busy at half time, he was busy stitching up both eyes, but Chris is fine."