Once-mighty Forest had not beaten Rovers in their last six games, during which period they had failed to score in all but one, and were starting to regard them as a bit of a jinx side.
It was Forest's biggest win of the season and Rovers' biggest defeat.
The scoreline, as is often the case, doesn't tell the whole story of the game - just that Forest were better on the day at taking their chances.
It was a bitterly disappointing result for Rovers just seven days after beating fourth-placed Queens Park Rangers at the Keepmoat Stadium
But while they remain difficult to beat at home, where they have lost just once, their record on the road is nowhere near as impressive.
Rovers have yet to record a win and have banked just four points from nine games.
The frustrating thing from Rovers' point of view, is that their paltry points tally nowhere near reflects how well they have played in the majority of their away games, and for them to lose by three goals will have come as a shock to the system.
To be fair, Forest are a decent side. No team goes on a long unbeaten run in the Champ-ionship, as they have, if they are't.
They are solid at the back, creative in midfield and have a strength in depth in attack that is the envy of a lot of clubs at this level.
Forest spent big money in the summer in a bid to try and ensure that not only was there no repeat of last season's relegation scare, but that they could make a start on the long road back to the top-flight.
The fact that they are now holding down a top-four spot suggests that it has been money well spent.
Had Sean O'Driscoll been able to keep hold of Richie Wellens and Matt Mills, and also had a similar amount of money to spend as his Forest counterpart Billy Davies in the close season, then who is to say that Rovers wouldn't also be hanging around the top six?
It remains to be seen whether the size of the defeat, more than their performance, will have an adverse affect on the self-confidence they take into every game in Saturday's match at Selhurst Park against a Crystal Palace side flying high.
Although Rovers trailed 1-0 at the break, they were still in the game and looked to have the momentum going into the second half.
Leading scorer Billy Sharp had missed Rovers' best chance of the half when shooting wide from close range following some impressive play by Dean Shiels.
Forest centre-back Kelvin Wilson, a one-time Rovers target, had put his body on the line a couple of minutes earlier to block a goalbound shot by James Coppinger and deflect it for a corner.
Forest had taken the lead on 17 minutes with a byline shot by Paul Anderson which took a deflection off Rovers defender Gareth Roberts.
There will have been many in the ground - especially the majority of the near-2,000-strong Rovers following sat behind the Forest goal - who will have questioned whether the ball was still in play before Anderson's cross into the box.
Rovers No 2 Richard O'Kelly certainly seemed to be unhappy with what he had seen and was subsequently sent to sit in the stand.
Prior to the goal there had been little between the teams.
Rovers had enjoyed the bulk of possession but were unable to turn it into chances - not least because they were being closed down quickly, causing various moves to break down.
Forest had seen far less of the ball but had looked the more dangerous side in the final third with the likes of Garath McCleary and Robert Earnshaw proving a handful.
The first goal of the second half was always going to be crucial.
Had Rovers scored first it would have been game on, but it was Forest who scored it - defender Wes Morgan heading home from a corner on the edge of the six-yard box on 59 minutes to leave the visitors with a mountain to climb.
Sharp had a chance to pull a goal back after James O'Connor had picked him out at far post with a right-wing cross, but he headed wide.
Earnshaw put paid to any lingering comeback hopes that Rovers might have entertained when getting on the end of Radoslaw Majewski's through ball just inside the area on 77 minutes and beating keeper Neil Sullivan with a low shot to his left.
Sullivan, who was carrying a slight knock, was immediately substituted with Ben Smith - fresh from a loan spell at Morecambe - coming on for his first taste of Championship football.
Unfortunately, Smith's first touch of the ball at this level was to retrieve it from the back of the net on 80 minutes.
Forest attacked down the right in a move finished off in style by substitute striker David McGoldrick, who beat Smith with a superb angled strike from the edge of the area.
Even though they found themselves trailing 4-0, Rovers didn't let their heads go down and
Sharp grabbed his seventh goal of the season on 82 minutes when beating Forest keeper Lee Camp with a header from Martin Woods' corner.
But the lack of celebration - especially compared to his goal against QPR - said it all.
It was never going to be anything but a consolation.


O'Kelly's View
I thought that we carried on from where we left off against Queens Park Rangers in the first half. and we moved the ball around very quickly.
If we had a fault it was that we didn't break lines and didn't get to the other side of them and produce enough of an end product, but you have to give Forest credit.



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