Saracens are on the verge of reaching the last eight of the Heineken Cup after a nail-biting Pool Five win over French side Biarritz at Vicarage Road.
The visitors led 6-3 early on but Sarries went in front through scrum-half Ben Spencer's fine try.
Owen Farrell added two penalties to give them a 14-6 half-time lead.
Dimitri Yachvili scored a converted try to give Biarritz hope but a brace of Farrell penalties, either side of a Yachvili kick, saw Sarries edge home.
Biarritz's losing bonus point mean that Saracens are not yet guaranteed a place in the last eight but a losing bonus point for the Londoners in their last game, away to Italian strugglers Treviso, would be enough to send them into the knock-out stages.
And a victory in northern Italy would put them in a strong position to secure a home quarter-final by finishing as one of the best four qualifiers.
While English champions Saracens are flying high in the English Premiership, Biarritz, despite an improvement in form since their big names returned after the World Cup, are struggling down in 12th in the French Top 14.
However, the visitors belied their lack of confidence to take an early 6-3 lead as Yachvili landed a penalty either side of a Farrell kick.
But the Saracens defence was putting the visitors under lots of pressure and experienced France scrum-half Yachvili was hustled into a series of errors, with his loose pass leading to Saracens' first try.
Twenty-year-old Farrell, playing his first game since being called into England's Six Nations squad, fly-hacked on and David Strettle and Ernst Joubert helped Chris Wyles set up a ruck five metres from the line.
Scrum-half Spencer, only 19, dummied to pass and sniped through a gap on the fringes before rounding Takudzwa Ngwenya to score a superb solo try.
Sarries nearly added a second score but Wyles was held up over the line after Mouritz Botha had intercepted a Yachvili pass.
However, with their pack getting well on top at the scrum, Farrell landed two more penalties to make it 14-6 at half-time.
Sarries looked in charge and, when Yachvili compounded his poor game by missing a chance to trim the gap before the break, it looked as though the visitors might fold in the second half.
Instead it was Saracens who lost their way and, with just under an hour played, Yachvili finally showed his class, charging down a kick by Peter Stringer, who had come on at scrum-half in place of Spencer.
Yachvili won the race to touch down, also adding the conversion to cut the gap to one point and set up a tense final 20 minutes.
A penalty apiece from Farrell and Yachvili meant the margin was still a single point going into the final 10 minutes.
But heroic defence from Saracens was enough to keep Biarritz at arm's length and Farrell drilled over a long-range penalty as the English champions kept on course for the knock-out stages.
Saracens director of rugby Mark McCall:
"We are pleased to have won the game - these kind of games are about getting the job done. There is a little frustration it wasn't more simple than it turned out.
"There were times in the first half and the start of the second where we were very dominant and at 14-6 we had an opportunity to pull away and break them.
"We couldn't do that but the last 20 minutes characterised everything we are about as a club with the the work ethic and discipline."
Saracens: Goode; Strettle, Farrell, B Barritt, Wyles; Hodgson, Spencer; Gill, Smit, Nieto, Borthwick, Botha, Brown, Saull, Joubert.
Replacements: Stringer for Spencer (56), Kruis for Botha (56), Stevens for Nieto (64), Wray for Joubert (67).
Not Used: George, Du Plessis, Powell, Short.
Biarritz: Balshaw; Ngwenya, Gimenez, Traille, Bolakoro; Bosch, Yachvili; Barcella, Terrain, Gomez Kodela, Thion, Taele-Pvihi, Lauret, Guyot, Faure.
Replacements: Heguy for Terrain (41), Marconnet for Barcella (49), Carizza for Taele-Pvihi (56), Peyrelongue for Bosch (56), Baby for Bolakoro (68).
Not Used: Guinazu, Roidot, Haylett-Petty.
Ref: George Clancy (RU).