The Blades were indebted to two on-loan players after closing the gap on Birmingham to three points in the Championship's race for automatic promotion with a 2-1 win over the relegation-threatened Tykes at Bramall Lane.
But a fourth successive league win for United was almost overshadowed by a fracas involving both dug-outs that saw Blades manager Blackwell and Barnsley counterpart Davey in groups that were forced apart by police.
Watford's John Joe O'Toole scrambled home his first goal for the club in the 81st minute and Italian striker Arturo Lupoli, of Arsenal, guided home the all-important match-clincher five minutes later.
Barnsley were awarded a last-minute penalty after Blades defender Greg Halford had handled, but goalkeeper Paddy Kenny kept out Jamal Campbell-Ryce's spot kick in fine style before temper erupted on the touchline.
Davey, who is convinced his side will again avoid relegation, said: "It was nothing really. I was disappointed with the multi-ball system. That was the issue.
"When Sheffield United scored their first goal all the balls disappeared. We had 24 when we were drawing and then there's one ball in the stadium when we're losing the game.
"I spoke to the referee and there were words exchanged, but it's nothing."
Blackwell, who refused to comment on the police's intervention, said: "I thought they wanted more time and I thought: 'Where's he going with this?'
"But I don't control the multi-ball system and it never went missing. I don't know what he's on about."
Blackwell added it was "another big win" for his side with five games left to play.
He said: "Tonight they (the top two) were looking and it's 0-0 with 70-odd minutes to go and then two goals go in, so psychologically they know that Sheffield United are chasing them.
"The lads have shown terrific spirit to chase them down because at one point Wolves were 14 points ahead, so to be as close as we are now is terrific credit to this side."
Blackwell hailed his skipper Chris Morgan as "fantastic" for his performance while under the spotlight.
The derby clash had been given extra spice in the build-up following events in the league encounter at Oakwell in November.
Barnsley striker Iain Hume spent a night in the high dependency unit of a Manchester Hospital with a fractured skull after being elbowed in the head by Morgan.
Blackwell said: "He was fantastic. Accidents happen. Nobody ever goes out to deliberately hurt anyone."
Davey added: "The referee handled the game really well.
"There's been a lot of talk in the press leading up to the game, but I felt the players from both sides and the referee (Grant Hegley) handled it very well."