Malang Sarr is set to join Porto on a season-long loan pending a medical this afternoon.
The 21-year-old French centre back joined Chelsea as a free agent in late August but the intention was always for him to go on loan for experience.
He was not given a squad number at Chelsea and has not been part of their coronavirus testing pool at Cobham, with Chelsea's website listing him as being on loan for several weeks despite nothing being agreed.
Bayer Leverkusen had previously shown some interest in the France Under-21 international, who left Nice at the end of his contract last season.
He joined the Ligue 1 side as a six year old and made his debut aged 17, making more than a cenutry of appearances.
But he did not agree a new deal and Chelsea felt he was a low-risk acquisition with potential for significant development.
"The goal is to have more playing time, to improve and be able to return [to Chelsea] to play," Sarr told Mercado Azul.
The future of Toni Rudiger, who has been relegated to Lampard's fifth-choice option at centre half, hangs in the balance.
The 27-year-old Germany international wants to play regularly and Tottenham Hotspur had shown some interest in signing him on loan but Lampard does not want to strengthen a rival.
Fikayo Tomori, meanwhile, will remain at Stamford Bridge and will be given further opportunities to impress having been tipped to go on loan earlier in the window.
Chelsea are also trying to move on one of Emerson Palmieri and Marcos Alonso but interest from a couple of Serie A clubs has not materialised into suitable offers as of lunchtime.
