Luton boss Mike Newell says the club had no choice but to let striker Steve Howard and captain Kevin Nicholls leave Kenilworth Road.
Howard has moved to Derby for £1m while Luton have agreed to sell midfielder a Nicholls to Leeds for £750,000.
"There is not a lot you we can do if these players want to leave the club," Newell told the club's website.
"Both were great servants but we have to move on. Hopefully I will be getting some of the money to sign new players."