Ashton, who joined the Saints in 2007, confirmed his intentions to the club earlier this week.
"We're obviously disappointed that Chris has decided he wants to play his rugby elsewhere," Mallinder said. "That said, we have known for some time that Chris was looking elsewhere and had been planning to use that part of the salary cap by strengthening our squad in a number of positions.
"We've also got several good wingers at the club who have all been pushing for a first team spot this season, the likes of Jamie Elliott, Vasily Artemyev, Scott Armstrong, Paul Diggin and Noah Cato, plus Anders Mogensen in the Academy who has been playing well on loan for Cambridge.
"They are all part of our plans going forward and will all contribute massively to the continued development of the Saints."
Following a specialist consultation yesterday Tom Wood will wear a protective boot on his left foot for four weeks to allow an injury to his big toe to recover.
The Northampton Saints and England medics will in the meantime work to treat Tom and monitor his recovery. Wood will attend next week's training camp in North Leeds.