The 24-year-old Spaniard left Camp Nou in favour of a move to Portugal last year, where the winger has endured a turbulent time, having been beset with a number of injuries.
Jeffren has started just one game for Lisbon so far this season, but that has done little to stifle Brendan Rodgers' interest, as he weighs up a bid to bring him to Anfield in the forthcoming January transfer window.
However, Liverpool will face competition for Jeffren's signature, from a host of different Premier League clubs, as his representative Jorge Llagostera told Portuguese radio station Antena 1.
"Yes. Liverpool and other Premier League clubs are monitoring the kid," he confirmed. "But, formally, we still not have received an offer to negotiate with Sporting."
Barcelona do retain a buy-back option on Jeffren, though the Spanish giants would be required to pay £9.6million to do so.
It's not yet clear how much Liverpool would be willing to pay for the forward, but with interest in his services believed to be high, Lisbon will be well placed to drive up the transfer fee.