Leinster head coach Leo Cullen offered an encouraging update on the fitness of Jonathan Sexton and Sean O'Brien after the pair lasted just 40 minutes of Leinster's 22-16 Champions Cup defeat by Montpellier.

Sexton, who has been nursing a tight hamstring, and  O'Brien both started, with the fit-again flanker involved in his first Leinster match since last January. While they were both called ashore at half-time, Cullen said the province were being "ultra cautious" with the pair.

"Johnny and Seanie, the two of them are coming back in. We're making assessments all week on those guys...on what's suitable and not putting guys at unnecessary risk," he said, with both players set to feature during Ireland's busy four-Test autumn schedule.

"The two of them came through and they were p****d off coming off at half-time. We're just managing them and being ultra cautious so hopefully they come through fine."

Cullen bemoaned the concession of cheap tries during his side's defeat at the Altrad Stadium.

Two of Montpellier's three tries came from Leinster errors in rain-soaked conditions, with centre Vincent Martin turning a Cian Healy knock-on into an opportunist score and man-of-the-match Nemani Nadolo doing likewise when intercepting a Jamie Heaslip pass.

In between, Fijian winger Nadolo bulldozed past Rob Kearney to help the French side lead 14-3 at half-time, but a smash-and-grab raid earned Leinster a losing bonus point thanks to captain Isa Nacewa's late converted try.

"It was a strange game, really strange. Those conditions were difficult and it led to it being quite a scrappy game in the first half in particular," Cullen said.

"I thought we were getting the upper hand even though we were playing into a reasonable breeze.

"For the most part we handled things really well, but then we get a really good turnover and give the ball straight back to them when they score (through Martin). It felt like a really cheap seven points.

"A couple of minutes later we defend a maul quite well to the sideline, but we defended quite narrow because of some of the threats they have and then Nadolo - it was really strong finish from him, we know the threat he poses.

"I thought the lads scrambled their way back into the game."

"Again the try in the second half (from Nadolo), we do really well to defend the maul, get a scrum from the turnover and we just cough up a cheap one.

"You have to be able to deal with things like that if you want to progress in this tournament."

With such a tight pool now - two points cover the four teams with table toppers Leinster leading Castres and Montpellier by the minimum - Cullen knows his charges can ill-afford to make the same mistakes in their December double header with Northampton.

However, the Wicklow man was pleased with the "fighting spirit" Leinster showed in battling back for that bonus point.

"I thought the lads scrambled their way back into the game," he said.

"Even after not getting over a couple of times, for Isa to get over at the end was pleasing and Isa's smart enough to get a little closer to the posts to make the conversion a bit easier."