And it is understood Pompey are concerned they will be unable to match what the resurgent Rams are currently tabling transfer targets.
Collins netted three goals in 30 games for Championship side Cardiff, yet retains an outstanding scoring record at previous clubs.
Now aged 31, he registered 72 times over four seasons and three divisions with Luton, establishing himself as a huge favourite.
During a previous spell with Swindon, Collins scored four in 22 minutes in a 5-0 win over Pompey on New Year’s Day 2013 in League One.
As it stands, the Blues are firmly in the running to bring the former Aston Villa youngster to Fratton Park.
However, Derby, who have emerged following nine months in administration, can offer more lucrative terms as they rebuild a squad which previously contained just five players.
At the end of last week, they announced the signings of Tom Barkhuizen, Joe Wildsmith and Nathaniel Mendez-Laing on two-year contracts, representing their first signings of the summer.
They will clearly continue being extremely active under interim boss Liam Rosenior as they play catch-up.
Importantly, Danny Cowley has not given up hope of tempting Collins to the south coast.
Yet he recognises he has a battle on his hands as he strives to add the in-demand frontman to a squad which has so far added just Marlon Pack and Zak Swanson following last season’s 10th-placed finish.
Since then, George Hirst has returned to Leicester City, while Aiden O’Brien rejected terms to stay, since joining Shrewsbury.
It leaves Cowley’s squad without a senior striker as they approach Saturday’s third friendly of their pre-season, with a fixture against Qatar SC.
A message from the Editor, Mark Waldron
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