Manager David Moyes said he might not have taken the job to manage Sunderland if he had known the club could be put up for sale and will have limited funds to invest in the squad.
Owner Ellis Short, who bought Sunderland in 2008, is willing to sell the club for 170 million pounds ($212.4 million), according to British media reports.
Moyes was tasked with pulling Sunderland out of a vicious cycle of Premier League relegation battles but has so far struggled to do so. The club remain rooted to the bottom of the table, four points from safety after 16 games.
Chief executive Martin Bain recently said that Sunderland will be unable to significantly strengthen in January and Moyes needs to rely primarily on the playing resources available.
"I did not know the club could be going up for sale. I was not made aware of that before. So that would probably be what I would say the difficultly is," Moyes told British media.
"I would have had to have thought a lot more about taking the job if I had known. Sunderland always had an appeal to me, but if I had known about the situation, I would have needed to look at it in a different way.
"I find that difficult because I have come here to improve the club. I don't want to be here and be a team at the bottom."
Sunderland, looking for the win that could take them off the bottom of the table when they host 11th-placed Watford on Saturday, have also been hampered by injury blows with Jan Kirchhoff being the latest to have suffered a cartilage tear.
He is their fifth midfielder now out of action.
"I didn't see us having no money. Even in the summer, I knew what we were spending was small in comparison (to others) -- and I said that to the owner, I said our spending was small," Moyes said.
"But I hoped it would be a short period and we would then have the next period (January) to get things done. That has shown itself not to be the case.
"I'm disappointed that I will not be able to do some work in January and try and build on what we've done."
($1 = 0.8004 pounds)
(Reporting by Shravanth Vijayakumar in Bengaluru; editing by Sudipto Ganguly)