Lawes is set to miss the opening clash against Wales on 6 February and the match with Italy a week later, while Lancaster’s back-row options are already stretched with Wasps lock Joe Launchbury and Gloucester No8 Ben Morgan already ruled out of the entire championship.
“This ankle has not settled down so I think he’ll probably need to have a little bit of surgery,” said Mallinder.
Bath boss Mike Ford, meanwhile, hailed a stunning contribution from England centre Jonathan Joseph as his side overpowered Pool Four leaders Toulouse yesterday to reignite their hopes of qualifying for the European Champions Cup quarter-finals.
Tries from wing Matt Banahan, scrum-half Chris Cook and Joseph fired Bath into a 25-15 lead at the break, despite France duo Yoann Huget and Yoann Maestri powering over in reply for the hosts.
A surging Joseph laid on a try for South Africa’s Francois Louw as fly-half George Ford successfully kicked three penalties, while Toby Flood replied with two of his own for the Top14 outfit.
Bath are now second in the table following their bonus-point victory, one point behind Toulouse, who travel to basement side Montpellier in their final pool game, while Bath host third-placed Glasgow.
“That last break by Jonathan Joseph was world-class and I’m pleased we finished it off with a try,” said Ford. “We get five points, they get nothing and we’re back in it. We’re a good side and we’re in a good place.”
Reigning Premiership champions Northampton face a Pool Five decider against Racing Metro at Franklin’s Gardens next weekend after eliminating Ospreys with a 20-9 success at Liberty Stadium.
Exeter Chiefs qualified for the European Challenge Cup knockout phase by ending a run of four consecutive defeats with a 33-24 victory over Connacht.