Middlesbrough's 'ridiculous' offer for midfielder George Saville was simply too good to turn down according to Millwall manager Neil Harris.
Saville, 25, joined Tony Pulis' side on a season-long loan last week, with a view to a permanent deal in January.
And despite Harris' desire to keep the Northern Ireland international, Boro's offer, which Millwall claim will be a club-record fee received for a player, was well above the midfielder's valuation.
"From a business perspective, George had to go," said Harris, who signed Saville from Wolves for £500,000 in 2017.
"The amount of money offered is ridiculous. From a business perspective, it's good business by us.
"John (Berylson, the club's owner) bought him for peanuts and sold him for millions and millions. As a manager, of course I've have loved to keep George - he did fantastically well for me.
"Once a player gets his head turned and wants to leave, it's difficult to keep somebody. No complaints about that. We acted in the market, thinking about George going, bringing in Tom Bradshaw and Ryan Leonard."
Boro saw a late bid for Saville rejected on the final day of the permanent transfer window, but Pulis was always keen to bring him to the Riverside.
Pulis has monitored Saville ever since the midfielder's youth days at Chelsea, and, according to Harris, the Teessiders will be getting a fine player.
“George is a brilliant lad, I had a really good relationship with George and when clubs like Middlesbrough, with the financial clout they have got and are able to take players at any price we set – it’s difficult to keep somebody.
Saville played 45 times for Millwall last season, scoring 10 goals, one of which came in the win over Boro at the Den.
The Lions went 17 games unbeaten towards the end of last season, a run which almost saw them sneak into the play-offs, before an eventual eighth-place finish.
Still, Harris is realistic about the club's position in the league's financial ladder.
“Expectation has risen at this football club because of how we over-achieved last year. But we have to be realistic about where we are. We are in the bottom three teams budget-wise and what we can pay individuals, if not lower than the bottom three.
“If players gets the chance to move on, we have to secure the best deal for our football club and we certainly did that.”
Meanwhile, Boro's home game against Derby on October 27 has been moved to a 12:30 kick-off and will be shown live on Sky Sports.