The 20-year-old defender was hurt during Rennes' 3-1 Ligue 1 defeat to RC Lens, falling awkwardly in the second half before leaving the pitch in visible pain. Rennes head coach Habib Beye admitted early signs were concerning.
"For Jeremy, it's his shoulder," Beye said. "We'll have time to see, but it's definitely quite serious."
Jacquet is set to join Liverpool at the end of the season after the Premier League club secured his signature in a 60 million pounds deal, including 55 million pounds upfront and 5 million pounds in performance-related add-ons. The France Under-21 international signed a five-year contract with the option of an additional year.
Liverpool beat competition from Chelsea to sign the highly rated centre-back after previously missing out on Crystal Palace and England defender Marc Guehi.
Reds head coach Arne Slot praised Jacquet's arrival, describing him as a "very big talent" and highlighting the club's work in securing his signature.
Jacquet, who has won five caps for France Under-21s, will remain at Rennes for the rest of the season before completing his move to Anfield.
Liverpool are currently dealing with defensive injury problems, with Giovanni Leoni, Joe Gomez, Jeremie Frimpong and Conor Bradley all sidelined ahead of their upcoming clash against Manchester City.
Liverpool defender and captain Virgil van Dijk expressed his joy with his teams hard fought Premier League victory against Sunderland at the Stadium of light on Wednesday.
Liverpool bounced back strongly to hand Sunderland their first home defeat of the Premier League season, edging a 1-0 win at the Stadium of Light.
Roberto De Zerbi has left his role as manager of Marseille by mutual consent, the club confirmed on Wednesday, following a string of disappointing results.
Tottenham have sacked head coach Thomas Frank after eight months in charge following Tuesday's 2-1 home defeat to Newcastle United.
