Mako Vunipola's early departure gave the British and Irish Lions an injury scare as Saracens over-ran Harlequins in a 40-19 Aviva Premiership victory at Wembley.
Vunipola lasted only four minutes into the second half before limping off with his knee strapped in a development which will concern Lions head coach Warren Gatland ahead of the squad announcement for New Zealand on April 19.
The England prop, who missed the start of the Six Nations with a knee problem, is a certainty for Lions selection if fit but he was at least able to rejoin his team-mates for a victory lap at the final whistle.
Saracens made light work of their London rivals in a niggly clash played out before a crowd of 71,324, powering ahead with first-half tries from Chris Ashton and Schalk Brits.
Owen Farrell kept the scoreboard ticking over throughout, finishing with a 20-point haul comprising of four penalties and four conversions, before Michael Rhodes and Alex Goode crossed in the final 10 minutes to register the bonus point.
Quins controlled territory and possession in the second half but until James Horwill drove over during the final throws of the match, they rarely threatened the try-line as their hopes of securing the last available play-off spot were dealt a blow.
The win leaves Saracens only one point adrift of second-placed Exeter and given their recent roll, the double winners are on course to secure a home semi-final after guaranteeing their place in the knockout phase for an eighth successive season.
Mike Brown was prominent during a feisty start that included a scuffle between the full-back and his England team-mate Farrell that started when Joe Marler slapped Rhodes in the face.
Harlequins lost Jack Clifford to a failed head injury assessment and in the 17th minute their task grew when Ashton claimed a poacher's try. Saracens attacked from a line-out with Duncan Taylor offloading in the tackle to keep the move alive, allowing Goode to chip ahead for Ashton to pounce when Brown failed to hold on to the ball.
Manful defence was enough to subdue the champions' pack on the whitewash but Quins reacted poorly to a rolling maul shortly after and Brits was driven over.
Nick Evans' third penalty kept the visitors in touch, but they would have slipped further behind had Ashton and then Sean Maitland held on to sloppy passes from Goode with the whitewash beckoning.
Goode dropped a simple catch, inviting pressure on to Saracens inside their 22, but Quins lacked meaningful ideas as they ran down blind alleys in search of a try.
It was a theme that continued into the second half and while the 2012 champions could at least claim to have dominated the third quarter, they never truly threatened to breach the defence.
Only Evans' accuracy from the kicking tee kept them in touch, but mechanical Saracens easily kept them at bay while never really exiting first gear. Farrell landed his third penalty and the 11-point lead survived Quins' next attack that began when Marland Yarde made inroads down the left wing.
Brown correctly had a try ruled out and Saracens took advantage of their absent-minded opponents to slip downfield, pinching line-out ball to allow Goode to send Rhodes over.
And in the closing moments the bonus point was delivered when Goode turned from provider to scorer, sprinting over to complete an emphatic win.