"Unfortunately, Pipey will be out for a few weeks," Thordarson told the Official Website.
"It is a blow to lose Pipey, a massive one. To be simple, Pipe hsa been one of our best players since the beginning of the season and is a vital member of the team.
"He is not only vital out on the pitch but in and around the squad and he will be sorely missed."
As well as Pipe, Dan Martin and Brian O'Callaghan - who both endured poor games at the weekend - will be missing from the squad that travels to Northampton for tomorrow's LDV Cup clash.
Martin suffered a cracked rib at Spotland and had to be removed at half-time, whilst O'Callaghan has picked-up a virus.