The Black Cats endured a horrendous start to the season, going ten games without a win.
They have improved in recent weeks, with victories over Bournemouth, Hull City and Leicester City under their belt.
The weekend saw them back at their worst, though, as they were comfortably beaten 3-0 by Swansea City.
That result saw them return to the bottom of the Premier League table and Redknapp did not hold back in his criticism of the current side.
“Every manager that has taken over at Sunderland has struggled, and that’s for one simple reason. The players aren’t good enough,” he told BT Sport.
“I think there’s every chance that this is the year they go down. David took over at the start of the year and he has inherited a very average group.
“He has not had the chance to put his team together and he has had to make the best with what he has, and when I look at them man for man, they are where they should be in the league.”
The January transfer window is certainly promising to be an interesting one for Sunderland.
It is fair to say that Moyes did not get the men he wanted in the summer and has had to rely on free signings so far.
With Sunderland bottom of the table and three points from safety, it is fair to say that things have not worked out well so far and a big January window may be needed to help them avoid relegation this season.