Sarries rub salt into the wound of Chris Robshaw's Six Nations Harlequins, the reigning English champions, finished a distant second in the northern reaches of their own city yesterday - and that was not the half of it. By the end, they had been chewed up, spat out and fed to the dogs. It was a horrible beating. Now they must head for Gloucester, another rugby venue straight out of the rugby lovers" version of Dante's Inferno, for a Friday night trial in front of the Kingsholm Shed. If they lose - and on this evidence, there is a real risk of them doing so - their place in the Premiership semi-finals will be far from assured. Poor old Robshaw must be wondering what the hell and why. Nine days ago, the flanker had the tantalising aroma of a Six Nations title in his nostrils, not to mention the heavenly scent of a Grand Slam. Now, all he can smell is ... well, you get the drift. He looked a weary player here and if this was understandable enough, given the extreme rigours and Herculean labours of his season so far, many in the sell-out crowd were surprised to see him being outplayed in every area of the pitch by the fast-developing Saracens breakaway Will Fraser. Yet those in the know were anything but staggered at this turn of events, for Fraser has been purple-patching his way through the Premiership for months now, to the extent that the England hierarchy are all but certain to include him in the red rose party for this summer's two-Test trip to Argentina. "It's hard to believe how far Will has come in the space of 18 months," said Mark McCall, the Saracens rugby director, enthusiastically. That was a top performance against a very good back row. It was a day that tugged hard on the Fraser heartstrings: his brother Henry, confined to a wheelchair after a holiday swimming accident, performed the ceremonial formalities as Saracens staged an official opening of their new stadium in Hendon. But once he settled to his work, he was outstanding - never more so than when he clattered the Harlequins hooker Joe Gray with a heavy tackle that dislodged the ball, leapt back to his feet in a split second, ran the best part of 50 metres as his fellow flanker Kelly Brown made big ground in enemy territory and then picked Owen Farrell's precise cross-kick out of the sky to register the game-breaking try. Fraser would have been under close consideration for the man-of-the-match gong but for another Saracens forward who has "World Cup 2015" written all over him. The unusually substantial Mako Vunipola, already a giant in physical terms but nowhere near fully grown in the developmental sense, turned in a performance of such startling productivity that George Osborne could legitimately have presented him as a transformative force in British industry. Certainly, the British and Irish Lions are beginning to see him in that light, and they could do far worse than take him to Australia in June for the headline event of the rugby year. More than anyone, Vunipola set the course of this top-of-the-table derby - a course Quins struggled to follow from the start and seemed less and less likely to complete as the afternoon unfolded. As early as the second minute, the loose-head prop picked an intelligent line on the shoulder of his fellow front-rower, Schalk Brits, and ploughed through both Robshaw and Danny Care to give Saracens a prime attacking position. When the Quins scramblers failed to roll away from the ball, Farrell opened the scoring with a penalty. Even though Nick Evans gave the visitors a semblance of a foothold with two penalties of his own, Vunipola's rampages in the loose told us all we needed to know about the probable outcome. He earned a second three-pointer for Farrell with a big bust off a line-out, then capitalised on a strong run from the No 8 Ernst Joubert to give the England outside-half the opportunity to spin the scoreboard again. If Vunipola had put Saracens in control by the end of the first quarter, the 2011 champions looked like certain winners by the half-hour mark. Farrell's intelligent short pass to Alistair Hargreaves split the Quins defence and after energetic contributions from Brown and Richard Wigglesworth, it was the hooker Brits who burrowed under a pile of pastel-shaded bodies to claim the opening try. For much of the game, it seemed as though nothing could go wrong for the home side. Unfortunately, they had Chris Ashton, the out-of-sorts England wing, among their number, so there was always the faint possibility of a big black cloud appearing smack in the middle of the silver lining. Sure enough, Ashton felled the Samoan back-rower Maurie Fa'asavalu - no easy matter, under any circumstances - with a swinging, throat-high tackle deep in the closing stages. Off he went to the cooler, his day well and truly done. He may not have heard the last of it, either. All things considered, though, he finished the weekend in a better place than Quins. "I don't really care about losing," said their director of rugby, Conor O'Shea, through gritted teeth. I do care when we don't show what we're about as a club. That was very definitely the case yesterday, and if they do not start showing the best of themselves soon, this once bright campaign might easily fade to grey. Kingsholm awaits, and it could be a season-defining moment. Scorers: Saracens: Tries Brits, Fraser; Conversion Farrell; Penalties Farrell 5. Harlequins: Penalties Evans 4. Saracens: A Goode; C Ashton, J Tomkins, B Barritt, D Strettle (C Wyles h-t); O Farrell (C Hodgson 76), R Wigglesworth (N De Kock 55); M Vunipola (R Gill 67), S Brits (J Smit 62, Brits 73), M Stevens (P Du Plessis 67), S Borthwick (capt), A Hargreaves (G Kruis 62), K Brown (J Wray 59), W Fraser, E Joubert. Harlequins: M Brown; U Monye, M Hopper, J Turner-Hall (G Lowe 54), S Smith; N Evans (B Botica 58), D Care (K Dickson 58); J Marler (M Lambert 63), J Gray (R Buchanan 47), J Johnston (W Collier 68), C Matthews (L Wallace 63), G Robson, T Guest (Lambert 20-27, M Fa'asavalu 51) C Robshaw (capt), N Easter. Referee: G Garner (Warwickshire).