Northampton set to miss out
Northampton scored a 13-3 win over Castres at Franklin's Gardens but retain only a mathematical chance of reaching the Heineken Cup quarter-finals.
With Leinster topping Pool 1 after scoring a comfortable 36-3 win over Ospreys in Friday night's other game, Saints can now only go through as one of the best two runners-up.
But that would require a string of results to go their way on Saturday and their chances of making the last eight look bleak, with the Amlin Cup now their most likely destination.
It was a struggle for Saints against a ferocious visiting defence and it took until the final minute for them to register what proved the only try of the game as George Pisi crossed.
Castres came to Franklin's Gardens with no chance of reaching the quarter-finals but made just one change to the starting 15 that lost to Leinster, with Daniel Kirkpatrick coming in for Remi Tales at fly-half.
Northampton brought Lee Dickson in at scrum-half with Samoan Fa'atoina Autagavaia making his first start for the club at full-back in place of the injured Tom Collins.
The home side looked for four tries from the start as they knew only five points and pointless defeat for Leinster would see them top pool one. They turned down easy penalty chances in the opening minutes, but a series of scrums did not produce a try.
Northampton were dominant at the scrum and after 27 minutes Castres tighthead Anton Peikrishvili was replaced by Mihaita Lazar and it was not clear that he was injured.
Despite that Castres were hard in the tackle and showed they meant business with even Courtney Lawes bent double by one hit from Piula Faasalele, plus they were disrupting Northampton's usually efficient lineout.
Castres thought they had taken the lead on 33 minutes when a quick lineout on halfway saw Remi Grosso scoot under the post, but referee Alain Rolland went to the TMO who spotted they had used a different ball.
Web-like Castres defence
Saints could not get into their attacking game, caught in the web-like Castres defence and in a half of just two penalties on the floor the second one saw Stephen Myler make it 3-0 on the half-time whistle.
Marcel Garvey almost got Castres on the scoreboard, with a superb 30-metre break, but the former Worcester flyer slipped as he looked to step round full-back Autagavaia and as the attack fizzled out Kirkpatrick put a drop goal attempt well wide. But when they won a penalty on 54 minutes, almost 50 metres out, Rory Kockott levelled the scores.
When Northampton needed a big shove from their scrum it deserted them five metres from the Castres try line, while Christian Day and Tom Wood made breaks on the left flank but twice the pass to George North went astray. And despite all their pressure it looked like they would fall behind when Kockott fired a 50m-plus penalty on target but his kick fell just short.
But with four minutes to go smart play from Kahn Fotuali'i saw the replacement scrum half throw a pass into Lazar's head and from the offside Myler slotted an easy penalty to make it 6-3.
And when Kockott was charged down by Pisi in his 22 the Samoan centre gleefully dived onto the bouncing ball to score the first try of the game in the final minute, which Glenn Dickson converted.