Nkunku, who left Leipzig for Chelsea in the summer of 2023 after being the Bundesliga's top scorer in 2022-23, is poised to return to the club where he enjoyed the best form of his career following unsuccessful spells in England and Italy.
According to Sky's Florian Plettenberg, RB Leipzig and AC Milan have reached a verbal agreement in principle for a loan with an option to buy, with only final details still to be settled and the move expected to be completed within two to three days.
The 28-year-old struggled to make an impact at Chelsea after an early injury disrupted his first season, and moved on to Milan last summer, where he scored eight goals and added three assists in 35 matches across all competitions.
He remains under contract with the Serie A club until 2030. Leipzig finished third in the Bundesliga last season and have identified further attacking reinforcement as a priority following Yan Diomandé's departure to Real Madrid.
That search has extended to Fernández-Pardo, with transfer expert Fabrizio Romano reporting that Leipzig have submitted a bid worth around €35 million, including bonuses, for the Lille winger.
The 21-year-old Belgium international impressed last season with eight goals and five assists in 29 league appearances, and is contracted to Lille until the summer of 2029.
Fernández-Pardo has also been linked with Bayern Munich, Borussia Dortmund, Liverpool, Manchester City, Manchester United and Aston Villa, underlining the scale of interest in the young forward.
Atlético Madrid tabled a bid of similar value, around €35 million, earlier this month, according to L'Équipe, though Lille president Olivier Létang was said to be pushing to negotiate the fee upward rather than accepting outright. Fernández-Pardo has made five senior appearances for Belgium.