Rennes manager Pierre Dreossi has hit out at departed captain Olivier Monterrubio.
Monterrubio made the switch to Lens just a few hours before the January transfer window closed on Wednesday in a deal which saw Olivier Thomert move in the opposite direction.
"He (Monterrubio) was in a failing situation and not very inclined to question himself," Dreossi told Ouest-France.
"For a few months he was not as good as he was before, we have seen it on the pitch.
"He was in a bad situation and hasn't been able to react since the beginning of the season.
"Olivier is someone that has a lot of difficulties in bouncing back. His name was playing more than himself. His performances weren't what we expected from him.
"As long as a player is competent with the club, he stays, if not, he leaves."
Lens director of sport Francis Collado told the club's website: "Olivier Thomert has definitely left the club. We recognise his talent and thank him for all the adventures he has experienced with us.
"We wish him well for the future and success with his new team."
In contrast to Dreossi's comments, Collado also reserved praise for new signing Monterrubio.
He added: "Francis Gillot (coach), Gervais Martel (chairman) and myself took the time to reflect on Olivier Monterrubio.
"We think we made the right choice. This boy will give a lot to the team thanks to his maturity. On the technical side he will help Lens progress."
Meanwhile Lens also captured the signature of Leiria player Damien Tixier before the window closed.
The left-back has penned a six-month contract with the club with the option to be extended for a further two seasons. He will replace Gregory Vignal, who is on loan at Kaiserslautern.
Lens brought in Milan Bisevac from Red Star Belgrade as well this week with Brazilian forward Jussie going on loan to Bordeaux.