The 23-year-old is currently on loan at Fenerbahce, who have the option to sign him outright during the summer as part of the deal.
However, Janssen could be sidelined for the rest of the campaign due to a toe injury, and Milliyet reports that the Super Lig side have been put off making the move permanent due to his injury problems.
Janssen's current problem has already seen him miss the last two months, and he has been limited to only nine league starts since joining from Spurs last summer.
The Netherlands international has scored only three times in his 12 appearances across all competitions this term and is now expected to return to North London once his loan expires at the end of the season.
Janssen also struggled to impress in his only full season at Tottenham, scoring just six goals in his 36 appearances for the club.