Neil Harris reckons Millwall need to show progression to keep top young players like Ben Thompson, Mahlon Romeo and Jake Cooper.
Middlesbrough tried to sign Jed Wallace last summer – in the end only taking George Saville to Teesside in a deal that could net £8million.
Glasgow Rangers publicly courted Cooper before the August window closed.
Both Wallace and Cooper signed new deals in the campaign just completed.
Harris said: “Will it [interest and speculation] be any different this summer? We haven’t performed as well. We’ve not taken the praise and publicity this year.
“It might be quieter for us, but we have still got some very good players and very good young players. People like Jake, Mahlon and Ben are really developing. If you want to keep your best players hungry and focused – and keep them – you have to keep moving forward as a club.
“We need to move forward and invest in the squad. We need to try and bridge the gap budget-wise from being second bottom in terms of budget to the six or seven clubs who might be above us budget-wise.”
Millwall have strictly adhered to Financial Fair Play and there is a feeling that some clubs in England’s second tier will be hampered next season by trying to cut their expenditure.
Birmingham were deducted nine points for breaching spending regulations. And Bolton Wanderers’ financial struggles have put the club’s very existence at risk.
“After two years as a Championship club we are not established at this level,” said Harris. “Two years at this level gives us experience. It means we know what we need to stay at this level and compete.
“We’ve not competed enough this year with the squad we’ve had, for various reasons.
“Finances certainly dictate when building the size of squad and the quality of players available. But you also have injuries and illness – that has been a big blow to us as well.
“We need a big turnover of players. We need an influx, certainly of players who have got experience of the level we play at.
“The gap between the clubs who spend money and can’t gets bigger and bigger. Competing for players, that makes it very difficult.
“We adhere to the rules, and rightly so. There are some clubs who will pay the price for not falling into line. I think there will be some clubs over the course of the next few months who have real tough spells – we are not going to be one of them.
“We’re in the fortunate position that we can rebuild.”
Conor McLaughlin and Tom King have both confirmed their exits – before they were officially announced by Millwall.
Right-back McLaughlin had an injury-disrupted last campaign in SE16 and could not displace Romeo when he was available.
King spent the first half of the season on loan at AFC Wimbledon.
Northern Ireland international McLaughlin tweeted: “After a great start, it turned out to be a couple of difficult seasons at Millwall but an experience I’ve learned a lot from.
“Thanks to everyone at the club, players, staff and fans for making me feel welcome from day one.”
King used the same social media platform to say: “The memories this club has provided me with over the last five years have been unbelievable – from the lows of relegation to the unrivalled joy of promotion two years later.
“From the fans to all the staff I’ve worked with I wish you all every success. See you soon.”