Mr Ashley was quoted by  The Times as saying "we can't make the same profit we made last year".
It also comes after he confirmed he would not give evidence in Parliament about how his workers are treated.
At close of trade in London, shares in Sports Direct International were down by 10.52% at 379.20 pence.
Mr Ashley was also quoted in the The Times as saying: "We are in trouble, we are not trading very well."
In July 2015, Sports Direct said profits for the year to 26 April were Â£300m, up from Â£249m the year before.
Meanwhile, MPs have repeated their call for Mr Ashley to be questioned by the House of Commons Business Select Committee in London.
Mr Ashley, owner of Newcastle United football club, has repeatedly refused to appear before the committee on 7 June, and offered instead to give MPs a tour of his head office in Shirebrook, Derbyshire.
Committee chairman Iain Wright said on Tuesday: "We expect Mr Ashley to attend on 7 June and to take this opportunity to respond on public record to the serious concerns regarding the treatment of workers at Sports Direct.
"We are still to receive a formal response from Mr Ashley to our invitation to attend. Select Committees rightly expect witnesses to attend evidence sessions."
He added: "Business leaders and others regularly appear in front of select committees when invited and we see no reason why Mr Ashley should expect to be exempt from the normal parliamentary process.
"Among other issues, we are keen to question Mr Ashley on the progress of the review he is leading on working practices at Sports Direct."
The committee now needs to decide whether to raise a complaint of contempt, and the House of Commons would then decide whether a contempt had been committed.
A BBC investigation in October 2015 found that ambulances were called out to the headquarters of Sports Direct 76 times in two years.
Many of the calls, for workers at the firm's complex at Shirebrook, in Derbyshire, were for "life-threatening" illnesses.
Former workers said some staff were "too scared" to take sick leave because they feared losing their jobs.
Sports Direct said at the time that it aimed to provide safe working conditions for all.
Shares in retailer Sports Direct have fallen by more than 10% after founder Mike Ashley was reported as saying that profits would not meet those of 2015.