The attacker represented Benfica between 2015 and 2019 before moving to Atletico in a big-money deal, and he has made 131 appearances for his current side in all competitions.
Felix spent the second half of the 2022-23 campaign on loan at Chelsea, though, before representing Barcelona on loan for the entirety of the 2023-24 season.
Barcelona continue to be linked with a permanent move for the Portugal international, who scored 10 times in all competitions for the La Liga side last term.
However, according to Correio de Manha, Benfica are currently in discussions over re-signing the 24-year-old for just £12.7m - a huge reduction on the £114m that they sold him for in the summer of 2019.
Felix's wage demands are believed to be problematic, but the Portuguese giants are allegedly hoping to get what would be one of the deals of the summer over the line.
The attacker is currently representing his country at this summer's European Championship.
Southampton 'stepping up interest in Delap'
Meanwhile, according to Football Insider, Southampton have accelerated their interest in Manchester City attacker Liam Delap.
The 21-year-old has a contract with the Citizens until June 2026, but it is understood that he is not in the plans of head coach Pep Guardiola for the 2024-25 campaign.
Delap spent the 2023-24 season on loan at Hull City, representing the Tigers on 32 occasions, scoring eight goals and registering two assists in the process.
The forward has been restricted to just six first-team appearances for Man City, also spending time out on loan with Stoke City and Preston North End during the early stages of his professional career.
Southampton are allegedly now stepping up their interest in Delap, with the Premier League champions thought to value him in the region of £20m.
Luton 'keen on loan deal for O'Brien'
Elsewhere, Lewis O'Brien is reportedly expected to leave Nottingham Forest this summer, with a number of clubs showing a desire to sign him.
The 25-year-old is said to be attracting interest from Ipswich Town, Sheffield United and Preston.
However, Luton Town have now joined the race, according to The Sun, with the recently-relegated outfit allegedly exploring a loan deal for the central midfielder.
The report claims that Norwich City are also keeping a close eye on the situation, with O'Brien not short of interest as he prepares to leave Forest once again.
The midfielder joined Forest from Huddersfield Town in the summer of 2022, but he has only made 17 appearances for the club, with his recent football coming on loan at DC United and Middlesbrough.
O'Brien, who has another two years left to run on his current deal, featured on 25 occasions for Boro during the 2023-24 campaign, while he has played 146 times in the Championship during his professional career.