The U's face the Black Cats who have stunned the Premier League this season, currently 11th in the table and looking on course to secure safety in their first season back since 2016/17.
After beating MK Dons in the last round, struggling Oxford face a tough ask to overcome an 'elite' Sunderland side.
"We would love to beat Sunderland and really kick on our season," Bloomfield admitted.
"We believe we can win.
"We know that we’re up against a really tough opposition.
Mark Harris shields the ball against Norwich City (Image: ©Jason Dawson)
"There are lots of clubs that have used cup competition as a springboard in their league form and if we can do that it’ll be fantastic.
"One big result can transform a season.
"We would love for that to happen for us on Sunday."
The Yellows go into the tie off the back of a disheartening 3-0 defeat at home to Norwich City on Tuesday night and currently sit 23rd in the second tier.
Sunderland manager Regis Le Bris lifts the trophy following the Sky Bet Championship play off final at Wembley Stadium (Image: John Walton/PA Wire)
Under head coach Regis Le Bris, Sunday's opponents reached the Premier League via the play-off final last season, beating Sheffield United 2-1, and invested heavily in the summer to give themselves a strong shout of staving off relegation.
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They have surprised everyone with their league performances so far, but it was less than a year ago that Oxford were beating the Black Cats 2-0 late in the campaign to avoid Championship relegation.
Oxford United players celebrate against Sunderland last season (Image: Mike Allen)
"[Le Bris] has done an incredible job," the U's boss declared.
"The squad is very, very strong and we know it’s going to be a big challenge whatever team they put out.
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"So, for us, it’s just about approaching the game in the right mindset, the right manner, and preparing properly.
"It’s about making sure that tactically we’re ready to play a really elite opposition.
"Physically the boys have recovered from Tuesday evening and we’ll pick a team that’s fresh to go and run because, ultimately, when you play these top boys, you have to run, you have to be at it for every minute.
United have managed to pull of some shock league results already this season with wins over Leicester City and Ipswich Town, but have struggled to pick up points against lesser opposition.
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"There have been results where maybe the result was unexpected and there have been some games where’s there’s been some hope for points, but it’s maybe not materialised," Bloomfield continued.
"That’s happened throughout the whole season and it’s definitely an area that we’re paying some attention to.
"There isn’t any expectation on us this weekend because we’re playing Premier League opposition and we want to show the best side of ourselves in front of our supporters and we want to get through the tie."