Bayonne 27-29 Connacht
Scrumhalf Caolin Blade scored two tries on his first start for Connacht as the Irish province struck late to beat Bayonne in France.
The French side had led since the third minute but a stirring second-half rally was capped by Blade's second touchdown on 76 minutes, which Miah Nikora converted to secure the points for the Irish province.
Connacht had changed all 15 starters from last week's comprehensive 42-19 victory over the same opponents in Galway.
Things looked ominous for the Westerners early on as Saimoni Vaka capitalised on a turnover to give Bayonne a third-minute lead.
Nikora reduced the deficit to four but Bayonne scored their second try as centre Mathieu Ugalde pounced on a chip for a 14-3 advantage.
On 28 minutes Blade scored his first try of the night after a break by Darragh leader.
Nikora and Christophe Loustalot swapped penalties and the hosts took a 17-16 advantage into the interval.
Pierre Sayerse scored Bayonne's third try from close range two minutes after the restart.
Captain Loustalot converted and when he dispatched another penalty Connacht trailed by 11 points with 20 minutes to play.
They swiftly forced a penalty at the breakdown, however, which Nikora kicked between the post, and he repeated the trick from inside 10 metres on 67 minutes.
With five minutes left, Nikora kicked for the corner and a lineout maul led to Blade touching down for his and Connacht's second try of the night.
Bayonne were behind for the first time and though they managed to force a late penalty, Ugalde sent it wide.
Connacht's keeps up the pressure on pool leaders Exeter and leaves them well-placed to secure a runners-up quarter-final spot.