Harlequins (10) 13
Tries: Care Cons: Evans Pens: Evans 2
Leicester (0) 17
Tries: A Tuilagi, penalty Cons: Flood 2 Pens: Flood
Leicester prop Marcos Ayerza locks horns with Harlequins counterpart Joe Marler in a brawl that saw both players sent off
Leicester moved seven points clear at the top of the Premiership by winning a feisty encounter with Harlequins which saw both sides finish with 14 men.
Quins led 10-0 at the break through a Danny Care try and Nick Evans penalty.
Tigers fought back to lead through Alesana Tuilagi and a penalty try, given when Quins had both Will Skinner and Mark Lambert in the sin-bin.
Props Marcos Ayerza and Joe Marler were sent off following a brawl before Evans and Toby Flood exchanged penalties.
Victory for Leicester once again extended their lead over second-placed Saracens, while defeat dealt Quins' hopes of making the play-offs a serious blow as, despite moving up to fifth with a losing bonus point, they now trail fourth-placed Northampton by eight points, but having played a game more.
Evans wasted the chance to give Quins an early lead when he sent a penalty across the face of the posts, while Nick Easter was denied a try by the video referee, who ruled his left leg was in touch before touching down.
Flood followed Evans' lead by hooking a penalty, awarded for pulling down a rolling maul, the wrong side of the posts and he was punished when Care made the most of a break down the left wing by Ugo Monye by spotting a gap near the posts and diving over.
Evans added the conversion and soon added a penalty when Leicester illegally halted an ominous maul.
But the Tigers came alive after the restart as Tuilagi squeezed in at the corner, Flood adding the conversion.
Quins were in trouble when the Tigers forced three penalties in succession close to the home side's line, with referee Wayne Barnes showing yellow cards to Skinner, for pinching the ball when he thought it was out, and Lambert, for collapsing the scrum.
Down the 13 men, Quins were unable to handle the next scrum and Barnes awarded a penalty try, with Flood's conversion making it 14-10.
Evans wasted a chance to cut the deficit by missing a penalty before Leicester prop Ayerza head-butted Quins counterpart Marler, who responded with a flurry of punches, resulting in both men being given their marching orders.
Fly-half Evans then landed a penalty to pull Quins to within a point but then blew another attempt to give his side the lead before Flood slotted a penalty of his own to secure Tigers' victory.
Harlequins rugby director Conor O'Shea:
"We're a good rugby side, and we created so many chances but we lacked the accuracy in execution. It was very frustrating to be honest.
"There are a number of talking points. Does Joe feel hard-done by? I know I would be. Should he have reacted that way, probably not. Was the provocation high? Absolutely.
"But I do want to know why when Tom Williams was tackled off the ball going for the line, there was no penalty try, no yellow card when both should have been 100%.
"You can write and be very accurate about what you saw. It was a huge game, but I have to go away, look at it again and be measured."
Leicester rugby director Richard Cockerill:
"That's rugby. So much happened out there and it was a fractious game at times.
"Marler was involved in everything. He has a Mohican hairdo dyed orange so he's difficult to miss. It's up to Quins to deal with him. We look to our own players.
"We certainly didn't look like champions in that first half and were fortunate not to be worse than 10-0 down. We spoke at the break about keeping to our game plan and doing things calmly."
Harlequins: Brown, Camacho, Lowe, Turner-Hall, Monye, Evans, Care, Marler, Gray, Andress, Kohn, Robson, Fa'asavalu, Robshaw, Easter.
Replacements: Williams for Monye (58), Lambert for Andress (43), Vallejos for Kohn (75), Jones for Fa'asavalu (57), Skinner for Robshaw (34). Not Used: Cairns, Moore, Clegg.
Sin Bin: Skinner (55), Lambert (56).
Sent Off: Marler (64).
Leicester: Hamilton, Agulla, M. Tuilagi, Allen, A. Tuilagi, Flood, Youngs, Ayerza, Chuter, Cole, Mafi, Slater, Croft, Newby, Crane.
Replacements: Smith for Allen (71), Castrogiovanni for Cole (58), Stankovich for Newby (68), Waldrom for Crane (58). Not Used: Hawkins, Woods, Grindal, Staunton.
Sent Off: Ayerza (64).
Ref: Wayne Barnes (RFU).