Although the U’s have only won two games, they have done it the hard way.
Their first-round tie involved two trips to Gateshead for a replay, while the weather intervened again to force two postponements at The Valley.
Ruffels has featured in all United’s games in the competition and believes the difficult run has had a positive impact.
He said: “I think it’s built our team spirit and we’ve fought a lot in this cup.
“We’ve done well, and if we beat a Championship side, it would be good for our morale and boost our confidence for the league.
“It feels like we’ve been in the FA Cup for a while and we don’t want to let it go.
“We’ll put up a good fight.”
Ruffels, 20, played well against Charlton last week and is pushing for another start tonight.
The midfielder, from Kidlington, is relishing a second chance to test himself against Championship players.
He said: “I don’t really see there’s much difference. I just play my own game and I’m confident enough in my own ability that I can face them.”
OXFORD United Women’s captain Sahara Osborne-Ricketts has signed a one-year contract ahead of their debut season in the FA Women’s Super League.