Chelsea have agreed a deal with Rennes to sign goalkeeper Edouard Mendy.
The Senegalese international, 28, is wanted by manager Frank Lampard to increase competition with club record £71m signing Kepa Arrizabalaga.
The Spanish international was also dropped last season after errors in games.
That included the FA Cup final, where the 25-year-old was replaced by second-choice goalkeeper Willy Caballero, who is 38.
Following the defeat at home to champions Liverpool, Lampard said Caballero would start the Carabao Cup tie against Barnsley at Stamford Bridge on Wednesday.
He added: “Kepa has to keep working and he has to have support around him, that's very clear.
"Individually players need support, particularly from myself, and I give that to all the players. And now we've got to try to give him confidence, because that's important.”
Last season for Rennes, Mendy kept nine clean sheets in 24 Ligue 1 appearances, compared to Kepa's eight cleans sheets in 33 Premier League appearances.
Mendy's save percentage was 76.3% and he conceded a goal every 114 minutes. Kepa's save percentage was 53.5%, conceding a goal every 63 minutes.
However, Kepa's passing accuracy was 79.7% compared to Mendy's 70.1%.
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