MK Dons made a mistake not investing in the squad with money from Dele Alli's sale, says boss Karl Robinson, after being relegated from the Championship.
Alli joined Tottenham in February 2015, but was loaned back to the Dons to help them win promotion last season.
"Nobody can turn around for one moment and say we could have kept Dele Alli," Robinson told BBC Look East.
"We probably should have used that some of the money to buy a striker or a buy a wide player or buy this or buy that."
Alli has since gone on to make six England appearances, and won the Professional Footballers' Association Young Player of the Year award for his performances for Premier League title hopefuls Spurs.
Robinson continued: "In the summer the most important thing was the announcement of a new training ground - these kids in Milton Keynes, the club is here for them.
"Without the training ground, Leicester, Norwich, Arsenal are coming in. Because of the success of Milton Keynes recently, a lot of external teams are coming into an area which was previously untouched."
Losing goalkeeper and goals hurt us
The Dons' 4-1 defeat at home by Brentford on Saturday confirmed their relegation back to the third tier after one season in the Championship.
Since Robinson's first-choice goalkeeper David Martin fractured his hand in training, the Dons have lost four and drawn two of their matches.
Robinson believes that is certainly a factor in their relegation, as well as missing loan players Benik Afobe and Will Grigg from last season's promotion-winning squad.
"We've not won a game since our number one goalkeeper has been out of the goal injured," said the MK Dons boss. "That's a massive loss to us.
"Probably a mistake of all of ours is not really investing to buy a player off the back of losing Dele Alli. And obviously Benik and Grigg went.
"For us to try to compete when you've lost 60-70 goals and go to a higher level, everyone said it would be an impossible challenge.
"But we pushed so far and got so close in certain games that there's a little bit of frustration we could have done something, even with all that negativity going before us."
Following Saturday's match, Robinson insisted he wants to stay on at a club he has managed since 2010.
But he added: "You've also got to say does the chairman want to sack me after getting relegated?
"I've not been brave enough to bring that up in any meeting. But what will be, will be. I know I have tremendous faith in me as a person and me as a football person.
"Getting relegated takes its toll on everybody. Sometimes this makes you better people. I think this little hardship at the moment will probably make me better than I was before."