Reading continued their perfect start to 2007 with a comprehensive win in the battle of the two sides promoted automatically from the Championship last season.
But Reading's impressive victory, their third on the bounce after a 6-0 thrashing of West Ham and an FA Cup win over Burnley, was marred by some ugly touchline scenes in the second half.
Royals coach Wally Downes and Sheffield United boss Neil Warnock, former team-mates at Bramall Lane, were both sent to the stands after Downes stormed into the Sheffield United technical area and shoved Warnock.
The heated exchange prompted an ugly touchline tangle and followed Keith Gillespie's sending-off, just seconds after coming on.
Those exchanges took the gloss off a Reading win secured by goals from Shane Long, Ulises De la Cruz, his first for the club, and Stephen Hunt. Christian Nade's reply came too late to spark a revival for the ten-man Blades.
Reading had the edge throughout in a scruffy match and were denied an early lead when Paddy Kenny palmed away a long-range effort from captain Graeme Murty, looking for only his third goal in nine years at Reading.
Kenny was back in the side after three weeks out with a groin strain and got involved in his fair share of debate.
The keeper was involved in some good natured banter with the Reading fans, but then squared up to Leroy Lita after the striker had raised a boot to run around the keeper and shoot into the side netting.
But there was little Kenny could do to keep out Reading's opener on the stroke of half-time as some calamitous defending in front of him let Blades down.
Lita and Hunt helped the ball into the path of Steve Sidwell, whose route to goal was crowded out, only for Chris Lucketti's clearance to cannon off Sidwell and into the path of Long.
It was a neat finish by the teenage striker, who turns 20 in two days time and Reading nearly doubled their lead seconds later.
Glen Little's far-post cross picked out Hunt's run and his header back across goal was superbly palmed away by Kenny at full stretch.
Five minutes into the second half though, Reading did put themselves in the comfort zone with a stunning goal from stand-in left-back De la Cruz.
The Ecuador international, only in the side at shot notice due to Nicky Shorey's absence through illness, won the ball in the left-back position and set off on a forward run before receiving a return pass from James Harper.
And De la Cruz kept his cool well, sprinting clear of a trailing defence and clipping a neat finish beyond Kenny.
The Blades responded by bringing winger Gillespie on for Derek Geary on 53 minutes, but the Northern Ireland international's appearance lasted a matter of seconds.
Almost from the moment he walked on the pitch, Gillespie was involved in a tangle with Hunt and lashed out, catching the Reading midfielder in the face.
Referee Mark Halsey showed a red card on the advice of his assistant, meaning Gillespie was off before he had touched the ball.
Gillespie compounded his dismissal by confronting Hunt on his way to the touchline, prompting an ugly row that flared up again minutes later.
This time, the war of words ended with Reading coach Downes walking into the Sheffield United technical area and shoving former team-mate Warnock.
Both were sent to the stand and, with the Blades rudderless and down to ten men, the visitors threatened to fall apart.
Hunt increased those fears when he cleverly hooked the ball into the roof of the net after Rob Kozluk had chested Sidwell's shot off the line.
But, to their credit, the Blades did pull a goal back when Reading's offside trap failed, allowing substitute Nade to poke home Stephen Quinn's free-kick.