According to The Northern Echo, Sunderland have concerns over appointing Daniel Stendel as their new manager.
It has been reported that Sunderland have interviewed Stendel, but the League One club are concerned that the German boss needs to clear his head having only recently parted company with Barnsley.
Following a run of 10 Championship games without a win, the Yorkshire club and the 45-year-old parted company earlier this month.
Sunderland dismissed Jack Ross as their manager earlier this month, with the results of the Black Cats far from impressive so far this season.
The Black Cats, who lost the League One final playoff at Wembley Stadium in London last season, are ninth in the league table at the moment with 19 points from 11 matches, as many as eight points behind leaders Ipswich Town and four points behind second-placed Wycombe Wanderers.
Sunderland will return to action on Saturday afternoon when they take on Wycombe away from home in League One.