But the Irish midfielder insists if the tie is still alive after Wednesday night's first leg at White Hart Lane, Nigel Clough's cup specialists will have "a brilliant chance" in the return leg at Bramall Lane.
Clough's Sky Bet League One side have beaten West Ham and Southampton to reach the last four and if that was not enough to serve Tottenham with a big enough warning, the Blades' exploits in the FA Cup these past two seasons add extra credence to their latest challenge.
"There's a lot to play for and I'm sure Tottenham will be fired up," Doyle said
"They'll look at our previous results and performances in other cup games and I'm sure they'll take note of that.
"They won't underestimate us, especially as we've come so far and they'll be looking to finish it in the first leg, so we've got to be on our guard.
"I just hope we can keep the tie alive
If we can, coming back to Bramall Lane will give us a brilliant chance."
Doyle led the Blades out at Wembley in last season's FA Cup semi-final defeat to Hull - Aston Villa and Fulham were beaten along the way - while this year West Ham and Southampton, in the Capital One Cup, and QPR, in the FA Cup, have all been despatched.
When asked to account for the Blades' imperious cup form, Doyle added: "I haven't got a clue to be honest with you, but since the Aston Villa game we've embraced everything about the cups and these ties.
"We've gone out with no fear in them and produced some of our best performances in a long time.
"The cup games have left people scratching their heads and asking why we can't replicate that form in the league.
"In the league games we probably have the ball as much but we sit back and counter-attack in the cup games a bit more, whereas teams probably do that to us in the league.
"It's quite difficult to play against if you do it right
We've found it difficult to play against at times, but we do it quite well ourselves, which we've shown against the Premier League teams.
"We're at the serious end of the cup now and probably nobody else will give us a chance, but our fans have seen the performances we've put in and they'll be expecting us to go down there and have a go."
Centre-half Chris Basham could go straight back into the starting line-up following his three-game ban, but midfielder James Wallace and Ben Davies (foot) are not expected to be involved and Ryan Flynn remains doubtful after missing Saturday's defeat at MK Dons due to an Achilles problem.
Source : PA
Source: PA