The 25-year-old made the switch to The Den during the summer of 2022 from Eredivisie outfit Fortuna Sittard and enjoyed a productive first campaign in England.
Flemming managed to find the net 15 times and provide three assists for teammates in 43 Championship starts, forming a brilliant partnership with fellow attacker Tom Bradshaw.
Despite performing above expectations under the leadership of former manager Gary Rowett, Millwall were unable to secure a top-six finish last season.
This term has proved much tougher for the Lions with Rowett and Joe Edwards both sacked over the course of the campaign, with Neil Harris now back in charge at The Den as Millwall look to avoid relegation.
Burnley back in the hunt for Millwall's Flemming?
According to Football League World, Burnley are likely to reignite their interest in Millwall attacker Flemming ahead of the 2024-25 term.
However, the report claims that a potential transfer for the Dutchman to Turf Moor is dependent on whether the Clarets suffer relegation this season.
Vincent Kompany's side are currently occupying 19th place in the Premier League table, six points behind Nottingham Forest in the relative safety of 17th.
It is understood that Burnley are more likely to target a move for Flemming should they be plying their trade alongside Millwall in the second tier next season.
It was widely reported last summer that the Clarets had a £7m bid rejected by the Lions for the 25-year-old, who was a standout player for Rowett's men in their ultimately-unsuccessful pursuit of the playoffs in 2022-23.
Burnley's transfer policy
Preparing for a return to the Premier League last summer, Burnley's transfer strategy was to recruit young players who have the potential to grow into top-flight stars.
With one of the smallest budgets in the division, the Clarets had to fish around Europe for largely-unknown talent, especially at the top level.
Luca Koleosho and Wilson Odobert - signing from Espanyol and Troyes respectively - are clear examples of this transfer policy over recent windows.
However, a move to bring Flemming to Turf Moor would signify a slight change in plan, with the 25-year-old already a proven performer in the Championship over the past two campaigns.