A series of shock results for the teams in the lower echelons of the division has left Bruce, whose side are second, particularly perplexed.
Last month Peterborough stunned leaders Cardiff, Birmingham inflicted a heavy 4-0 defeat on promotion hopefuls Crystal Palace while Barnsley and Blackpool both claimed victories over third-placed Watford.
And while the Hornets' victory at the KC Stadium on Tuesday night stopped Hull grabbing the initiative in the pursuit of the second automatic promotion spot, Bruce is expecting more upsets over the final half a dozen fixtures.
Bruce's men face four of the current bottom eight before a potentially pivotal final-day meeting with Cardiff.
Asked if their fate could be decided on May 4 when the Bluebirds come to the KC Stadium, Bruce said: "Last game? It's possible. Who can predict it?
"We'd all be guessing but the Championship throws up, as we've seen in the last three or four weeks, result after result that is scratching-your-head stuff.
"The teams at the bottom are the form teams, so it's all to play for."