The game comes just two days before Welsh face a Rugby Football Union disciplinary hearing that could play a huge part in deciding their Premiership fate this season. Welsh, currently one place above bottom club Sale, will need to explain why scrum-half Tyson Keats, who starts on Sunday, featured in nine Premiership games this season when he was not eligible. A sizeable points deduction might await.
The immediate concern, though, is bouncing back from last weekend's 47-16 thumping against Exeter, and centre Seb Jewell said: "All season long we have been a positive team. We are not the sort of team to take defeats to heart, so while we have struggled to get results of late we know there is no point in wallowing."
He added: "Avoiding relegation is still in our own hands at this stage, so we take that as a real positive."
London Welsh show a number of changes from the side crushed by Exeter.
Gonzalo Tiesi, Neil Briggs and Ed Jackson are all injured, but new signing Seb Stegmann makes his debut on the wing.
Prop Greg Bateman moves to hooker instead of Briggs, with James Tideswell featuring at tighthead, and other starters up front include lock Kirill Kulemin and number eight Alfie To'oala.
Saracens boss Mark McCall has made just two changes to the side that won at Leicester last weekend, with Duncan Taylor at inside centre and George Kruis chosen as skipper Steve Borthwick's second-row partner.
Flanker Andy Saull, meanwhile, is in Saracens' match-day squad for the first time since fracturing his thumb before Christmas.
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