La Rochelle captain Will Skelton said his side "weren't good enough" after they were beaten 25-24 at Castres in the French Top 14 on Saturday a week after being knocked out of the Champions Cup quarter-finals.
The two-time Champions Cup winners, coached by former Ireland fly-half Ronan O'Gara, were hammered by Leinster last Saturday but still move up to fourth in the French table thanks to the bonus point with five rounds of the regular season to play.
"We wanted to send a message here, but we weren't good enough," Australia lock Skelton told reporters.
"We were very proud to play the quarter-final of the best club competition in the world, the emotion was high, and the fall after was just as steep," he added.
Young winger Nathanael Hulleu crossed twice in eight minutes for the home side, who moved up to sixth place, the final play-off spot, with their first win in five games in all competitions.
Former New Zealand scrum-half Tawera Kerr-Barlow was missing for O'Gara's side after suffering a head knock against Leinster.
Despite Kerr-Barlow's absence, La Rochelle led 14-13 at the break thanks to an impressive solo try from Samoa center UJ Seuteni.
Hulleu's double in the final 15 minutes swung the game in Castres' favor as the 23-year-old took his try tally to nine for the season.
Elsewhere, leaders Stade Francais needed an 81st-minute try from No 8 Giovanni Habel-Kueffner to beat Bayonne 28-24.
At the other end of the table, bottom side Oyonnax moved nearer to relegation losing 43-13 at home to third-placed Racing 92, thanks to 18 points from South African full-back Tristan Tedder.
The Springboks' two-time Rugby World Cup winner Siya Kolisi was missing with an ankle injury for Racing in the week he was named among Time magazine's 100 most influential people of 2024.
Australian fly-half Jake McIntyre scored 19 points as Perpignan moved closer to safety hammering Lyon 51-20.
Later, second-placed Toulouse are without Antoine Dupont as they face Toulon at Marseille's Velodrome with the scrum-half again away with France's sevens set-up before this summer's Olympic Games.
On Sunday, Bordeaux-Begles host Clermont a week on from their heartbreaking one-point Champions Cup loss to Harlequins.