Hull have endured a miserable 10-match winless run - their last victory coming over Crystal Palace on October 4 - leaving them second from bottom at Christmas.
The barren sequence comes despite heavy investment during the last transfer window, with the likes of Abel Hernandez, Gaston Ramirez and Mohamed Diame all moving the KC Stadium.
Bruce admits that he is going through his toughest period as Hull manager, but he is adamant the club can move up out of the relegation zone and improve on a 16th-placed finish in the 2013-14 campaign - their highest ever placing in English football.
"Of course it's been the most difficult [period]," he said. "We've been here two-and-a-half years and if we think it's all going to go one way we're kidding ourselves.
"It's incredible how three or four losses can turn into not winning in 10 or whatever it is.
"We have to get back to winning ways. The squad and myself, nothing has changed.
"It's amazing what a win and a bit of confidence can do, let's hope it's in the near future and we can get our season back on track because I'm still convinced we can finish above where we did last year."
Part of Hull's troubles has been the absence of several key players and the likes of Michael Dawson (hamstring) and Diame (knee) miss Friday's trip to the Stadium of Light through injury, prompting the recalls of Tom Ince and Maynor Figueroa from respective loan spells at Nottingham Forest and Wigan Athletic.
Midfield duo Tom Huddlestone and Jake Livermore also miss out through suspension.
Bruce, who is without an assistant manager after Steve Agnew departed for Middlesbrough on Tuesday, also stated that Paul McShane is unlikely to come back into the first-team until the defender issues an apology following reports of a falling out between the pair.
Despite their recent woe, Hull can take confidence from the fact they beat Sunderland three times last season - including a 2-0 triumph in February's corresponding fixture in the previous campaign.
Gus Poyet's side head into the match with a huge morale boost, though, after Adam Johnson's 90th-minute winner earned a 1-0 derby victory at Newcastle United on Sunday.
The victory marked a fourth straight success over their local rivals and provided a timely three points, with Sunderland having won just three times in the league this term.
Head coach Poyet has injury concerns of his own, particularly at left-back with first choice Patrick van Aanholt (shoulder) unavailable and Anthony Reveillere - who had been filling the void - joining him on the sidelines with a calf complaint.
Billy Jones could take the position after stepping up his recovery from a hamstring problem.
However, forward Connor Wickham is unavailable through suspension.
