The fiery contest in Nantes was settled by the immaculate goal kicking of Owen Farrell as he punished Racing indiscipline with 10 penalty goals - though Sarries were not entirely blameless and had to do it the hard way after twice being reduced to 14 men with Will Fraser and Chris Ashton spending spells in the sin bin.

Farrell kicked everything that came his way, including the conversion of full back Chris Wyles' try, after Farrell had inevitably provided the platform for the score from a line-out with his pin-point touchfinder.

The win took Steve Borthwick's team to 18 points with a regulation win at home against Edinburgh Rugby on Sunday good enough for a last eight place.

Racing are now out of the hunt on 12 points - Farrell's final last-gasp penalty denying them even a sniff of a losing bonus point - and Munster, who play Edinburgh at Murrayfield in their Round 5 game, are the only remaining threat for group honours.

But it was Farrell's masterclass with the boot that decided this make-or-break contest as Racing outscored them 3-1 in tries.

Prop Luc Ducalon got the first after just six minutes and Pumas wing ace Juan Imhoff got two in just four minutes at the end of the first quarter.

It all added up to Saracens finding themselves 13 points adrift three times before they steadied the ship and staged a fightback brimming with never-say-die character.