Weekend Premiership preview: Extra spice added as Sarries meet Quins in tasty top of table encounter It is fair to say that Harlequins, the reigning English champions, did not perform cartwheels of joy when Saracens, their immediate predecessors and chief rivals for this year's title, secured the services of the Samoan prop James Johnston for next season. Quins have some mighty contributors - Chris Robshaw, the national captain, for starters - but Johnston's stabilisation of a dodgy scrum has been at the heart of their surge up the domestic rankings. The Londoners did not want to lose him, least of all to a team from the wrong side of the Thames. Saturday's first-versus-second rumble at Allianz Park, the new Saracens stadium in the northern reaches of the capital, was always going to be a heavyweight bout. With Johnston facing the fast-improving red rose prop Mako Vunipola in the darkened recesses, the weight is now off the scale. The two giants may well meet again before the formal joining of forces at season's end - perhaps in the Premiership final at Twickenham in May - but this confrontation will be no less gripping for that. Send for the full metal jacket. All of those who found themselves overwhelmed by the Welsh rebellion in Cardiff last weekend are present and correct: Alex Goode, Chris Ashton, Brad Barritt, Owen Farrell and Vunipola for the home side; Mike Brown, Danny Care, Joe Marler and Robshaw for Quins. Interestingly, Leicester are also throwing their England contingent - the half-backs Toby Flood and Ben Youngs, the forwards Tom Youngs, Dan Cole, Geoff Parling and Tom Croft - straight back into the fray at Exeter this evening, even though one or two of them seemed wearied by the intensity of the Six Nations campaign. There is no rest for the wicked, or indeed for anyone else. If the collision between the top two has been the main subject of discussion in Premiership circles this week, there are a couple of significant matches at the other end of the table. London Welsh, still wondering exactly where they stand on the disciplinary front after Thursday night's inconclusive appeal hearing against a five-point penalty for breaching eligibility regulations, will do well to take anything out of Gloucester at Kingsholm, especially as the West Countrymen have Freddie Burns and Billy Twelvetrees pulling the strings in midfield. London Irish, on the other hand, could take a big step towards addressing their own relegation issues by beating Worcester, hardly the greatest travellers in the world, in the St Patrick's Day-linked jamboree in Reading. The Exiles will be led by the former Wasps and Leicester lock George Skivington, who yesterday applied his thumbprint to a contract keeping him at the club until the end of the 2015-16 season. Wasps, meanwhile, will run another member of the Vunipola family, the No 8 Billy, in a tidy-looking loose combination against Northampton this afternoon. Stuart Lancaster, the England coach, is desperate to give the youngster an early taste of international rugby. Today, we may discover why. Table and weekend fixtures Sale v Bath Saturday (3pm unless stated) Gloucester v London Welsh London Irish v Worcester Wasps v Northampton (3.15) [Sky Sports 1] Exeter v Leicester (5) [ESPN] Saracens v Harlequins (2) [ESPN]