Blues draw comfort from 'home quarter'
Leinster lose Sexton and Nacewa to injury but Aviva tie looks secure
It will take a Connacht miracle to deny Leinster a home quarter-final in the Champions Cup.
Last week, they became the first club to breach the barrier to the quarter-final.
Last night, they became the first to almost certainly ensure that will take place in their home town.
The Irish province was last at Stade Pierre Antoine in October 2014 when they had to weather a storm to come through it.
It would be no different this time as the French were all set to defend castle Castres. The home side showed their intent, raiding down the right. Robbie Henshaw had to be vigilant to see-off Antoine Dupont.
Somehow Leinster lost their ruck ball and flanker Yannick Caballero fumbled it forward.
The front row, anchored by Tadhg Furlong, crunched out a penalty.
They moved play over and back before Isa Nacewa dribbled a ball to force a lineout out of full-back Pierre Berard.
The platform was accompanied by the patience to work the phases, Josh van der Flier and Garry Ringrose's tip-on passes important to drawing out a penalty which Jonathan Sexton struck in the ninth minute.
Then, their hard-up defence from Ringrose and Robbie Henshaw forced a mistake out of Julien Ciminati. Ringrose picked up and parted with the ball for Henshaw to take off from inside his own half for a try, Sexton converting.
They came again from the restart as Adam Byrne spectacularly fielded the ball above his head.
But, Leinster twice ran into trouble from their exit strategy, requiring Furlong's big hit on David Smith and a Devin Toner lineout steal to defuse the danger.
It didn't last long. Scrum-half Dupont's change of direction and out-half Julian Dumora's conversion changed the momentum of the game in the 22nd minute.
As Johnny Sexton was being treated, Ross Byrne almost created a try for Rory O'Loughlin, but for a foot-in by Berard.
A loose clearance from Nacewa invited pressure and David Smith's outrageous stepping almost worked the oracle, Dumora's penalty tying it up.
The missed tackles were mounting up and the injuries too as Nacewa joined Sexton on the sideline.
Florian Vialelle fended off Ringrose to create a two-on-one finished by Smith.
Dumora landed the conversion for 17-10 in the 36th minute.
Leinster needed a response and they got it from flanker Jack Conan's burst down the middle. They just couldn't finish what he started.
On resumption, Ringrose was on a mission, scything through the first line of defence to provide position.
The scrum gave the platform. Adam Byrne steamed over the top of Dupont from first receiver and Henshaw was on his shoulder to duck inside wing Smith at the posts.
Ross Byrne's simple conversion made it all square in the 43rd minute.
Rob Kearney immediately broke from deep only for Luke McGrath to spill the ball.
This signalled Castres' return to the front-foot for a stunning series of phases that concluded with Smith plunging to the line for Dumora to make it 24-17 in the 53rd minute.
A typical Toner block on Dupont and Conan's fight for the ball was the seed for an attack spoiled by James Tracy overthrow at five-metre lineout.
It took Adam Byrne's break and Conan's offload for Jack McGrath to go close. Castres conceded a penalty and referee Greg Garner showed Berard a yellow card.
Dan Leavy was sprung from the bench and Tracy's cleanout allowed the former's low body angle to take the flanker over for Ross Byrne to level the game in the 65th minute.
Full-back Berard returned without further damage done on the scoreboard and the French drove forward through the maul and hard runners.
Mike McCarthy was just on the field for Ross Molony when he was carded for illegal work at the maul.
Leinster reacted well in adversity as O'Loughlin and Jamison Gibson-Park combined to turned Castres maul into their scrum.
There was one final chance to strike from a lineout, Gibson-Park opting to kick the ball into touch to end the game.
Castres 24 Leinster 24