France full-back Brice Dulin said La Rochelle will have to improve ahead of next month's European Champions Cup semi-final with Leinster after Saturday's 38-23 home win over Lyon in the French Top 14.
Dulin's men missed out on the chance to go top of the table as they failed to claim a bonus point despite South Africa winger Dillyn Leyds scoring a try and creating another.
Joint-record four-time European champions Leinster head to Stade Marcel-Deflandre on May 2 in the hosts' first ever continental last four tie.
"The matches that are coming over the next weeks and months will be even harder," Dulin told Canal+.
"The semi-final will be played on the small details, mistakes. We have very little time to prepare.
"We have to capitalise on what we've done already. It will be a chess match, we have to be stronger physically and mentally to deal with their attacks," he added.
It is unlikely that Jono Gibbes' outfit will have a game next weekend ahead of facing the Irish province, who are led by Ireland captain Johnny Sexton.
Brive, who La Rochelle are scheduled to play on Saturday, recorded numerous Covid-19 cases last week.
On the Atlantic coast, Gibbes' men started at a canter as Leyds crossed for his eighth try of the season after a delicate Dulin chip before Ihaia West added the conversion.
The hosts led 20-6 at the break after West crashed over with the clock in the red.
The outside-half failed to return to the field after the interval after hurting his shoulder in scoring.
Leyds became the provider five minutes into the second half as his one-handed slap-pass set up centre Geoffrey Doumayrou.
On the hour mark, Ireland three-quarter Darren Sweetnam came on for his La Rochelle debut after signing as injury cover two weeks ago.
Former New Zealand scrum-half Tawera Kerr-Barlow then left the field with a neck issue to add to Gibbes' fitness headaches ahead of the semi-final in two weeks' time.
Fiji winger Josua Tuisova scored his 50th and 51st league tries for the away side to deny La Rochelle the bonus point, which would have moved them top.
- Castres win derby -
Earlier, Toulouse full-back Matthis Lebel might have scored a contender for try of the season, but it was not enough as Castres held their nerve to claim a 26-24 derby scalp.
France U20s back Lebel and Zack Holmes were the only two in Toulouse's starting lineup to have played the leaders' Champions Cup quarter-final victory last weekend at Clermont.
Of the matchday squad involved in the win in the Auvergne, 13 didn't even make the trip for the derby in southwest France, with the likes of South Africa's Rugby World Cup winner Cheslin Kolbe rested.