Leinster were relieved to leave Lyon with their winning record intact in the European Champions Cup after a nervous end to their win in Stade Matmut de Gerland.
A solitary from number 8 Max Deegan shaded a Pool 1 clash in which the Leinster’s defence prevailed against a hard-running home side that was just short on finishing power.
“We knew it was going to be tough so there was no major surprise, but we got the job done,” admitted Leinster head coach Cullen.
“We can now turn our attention to Glasgow away in the PRO14 and back-to-back games against Northampton will be a great challenge for us.
The boot of Johnny Sexton gave Leinster an early lead after withstanding the first flush of Lyon intensity in the opening minutes. Another a few minutes later he was invited again but his penalty hit the post.
Lyon spent much of the opening quarter in the Leinster half but precious little got past the blue wall. Meanwhile, the most enervating Leinster move coming from Robbie Henshaw on 15 minutes. The Ireland centre saw space and made the break but with James Lowe on his outside shoulder Henshaw stepped into contact and the moment was lost.
While Lyon dominated territory and possession, Leinster remained patient. Their first chance arrived when Josh van der Flier blocked down out-half Jonathan Wisniewski to feed James Ryan for a gallop up the park. Van der Flier was up fast cleaning out inside the Lyon 22 as Leinster picked and drove. Five phases later Max Deegan, with Rhys Ruddock aiding, ran through hooker Mickael Ivaldi for a try against play with Sexton converting for 0-10.
All going to plan for Leo Cullen’s side, and even when Jordan Larmour was binned for diving in from an offside position, Lyon could not get on the scoreboard.
Lyon number 8 Carl Fearns was causing problems and scrumhalf Baptiste Couilloud was endlessly sniping forward, Rob Kearney covering wonderfully to put the Lyon captain into touch from an attacking kick and chase on 32 minutes.
After almost five minutes of frantic tackling inside their 22 in the closing minutes of the first half Leinster went into the break rightly proud of a defensive master class and that Lyon had nothing to show for all their territory and possession.
Leinster also knew that both the lineout, where two were lost, and the scrum were coming under some pressure from an unrelentingly up-tempo home side.
Just past the hour a huge turnover from Andrew Porter on Fearns as Lyon tried to maul their lineout drew enthusiastic slapping from Leinster, who were coming under pressure.
A penalty from captain Wisniewski on 67 minutes to close the gap to 3-10 laced the final 10 minutes with an edginess for the visitors.
Sexton believed he had silenced the crowd on 75 minutes when he went under the posts only for a referral to show Garry Ringrose had obstructed a tackle.
An exchange of penalties in the closing minutes franked the away victory for Leinster, on a scoreline of 6-13, leaving Lyon frustrated and schooled on the virtues required to achieve success in Europe.
LYON: T Arnold; X Mignot, T Regard, C Ngatai, N Nakaitaci; C Wisniewski, B Couilloud (capt); X Chiocci, M Ivaldi, D Bamba; V Bruni, H Roodt; J Puricelli, L Gill, C Fearns.
Replacements: L Goujon for Puricelli (30); R Chaume, F Kodela for Chiocci and Bamba (both 47), J Maurouard for Ivaldi (53), J Pelissie for Couilloud (53), E Oosthuizen for Roodt (66), R Wulf for Mignot (69).
LEINSTER: R Kearney; J Larmour, G Ringrose, R Henshaw, J Lowe; J Sexton, L McGrath; C Healy, R Kelleher, T Furlong; S Fardy, J Ryan; R Ruddock, J van der Flier, M Deegan.
Replacements: D Toner for R Ruddock (53), A Porter for Furlong (53), J Gibson-Park, J Tracy, E Byrne for Mc Grath, Kelleher and Healy (all 61), R Byrne for Fardy (72), R Byrne for Sexton, D Kearney for R Kearney (both 78)
Referee: L Pearce (RFU).
(c) Irish Times service