Abdulmalik is supposedly one of them, having yet to sign a new deal at the Den.
He has been offered fresh terms to remain with the Lions but is exploring his options heading into the 2021-22 season.
Abdulmalik has yet to make his senior debut but has been a regular for Millwall's under-18s and under-23s in recent years.
He's also supposedly been in high demand in the past. It's reported that the Lions turned down a bid from Swansea City which was viewed as ‘derisory’.
Meanwhile, Premier League heavyweights Arsenal, along with Old Firm duo Celtic and Rangers, have also been linked with moves this summer.
Should the Blues opt to sign Abdulmalik, they'd have to pay a compensation fee to Millwall as he is under the age of 24.
Cowley is looking to supplement his squad with fledgling squads following an academy player clearout at the end of last season.
The likes of Harry Kavanagh, Charlie Bell and Harvey Rew were released, while Alfie Stanley turned down a new contract.
Pompey have already signed 18-year-old Liam Vincent for an undisclosed fee from Bromley.
He's expected to head out on loan to garner more first-team experience, having played seven times for the Ravens last season.