Struggling Wigan slipped to their fifth Premiership defeat in a row as Blackburn won a scrappy Lancashire derby at the JJB Stadium.
Derbyshire (left) celebrates his first goal for in-form Blackburn
After going close twice for the hosts it was Emile Heskey who gave Blackburn the lead, nodding into his own net from Morten Gamst Pedersen's free-kick.
Substitute Matt Derbyshire doubled the lead, volleying in from two yards after Pedersen's clever header across goal.
Benni McCarthy's penalty wrapped it up after Fitz Hall handled in the area.
It was Blackburn's third win in succession and completes a remarkable turnaround in their fortunes after a 6-2 drubbing at Arsenal just nine days ago.
In truth it seemed an unlikely outcome after Wigan made a promising start to the game, with Heskey in particular a real danger.
Just 10 seconds in he nodded over a Dave Cotterill cross, before meeting a Leighton Baines centre by flicking the ball with the outside of his right boot narrowly wide.
Brad Friedel was then called into action to parry away Josip Skoko's stinging half-volley from 20 yards as Wigan continued to press.
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But as the half wore on and the rain began to lash down, the torrential conditions started to have a real effect on the already weary players, some of whom were playing a fourth game in 10 days.
Blackburn's main threat was from David Bentley down the right, but he was not seeing enough of the ball to cause the hosts that many problems.
Indeed it was against the run of play that Rovers went in front and Heskey finally got his name on the scoresheet - albeit at the wrong end.
The burly striker headed into his own net under pressure from Zurab Khizanishvili after Pedersen's inswinging free-kick from the right.
It was harsh on Heksey, who had been his side's major weapon going forward and he tried to make amends straight after the break with a volley that Friedel comfortably collected.
Wigan were still dominating possession, but simply could not convert any of their chances, Baines blazing a free-kick wildly over from the edge of the box.
Just before the hour mark, Blackburn made them pay again. Lucas Neill chipped a ball into the box and Pedersen cleverly headed it across goal for Derbyshire to volley in his first goal for the club.
Not that there was a particularly big groan from the home fans - after all, only 14,864 had bothered turning up for this Lancashire derby.
The visiting fans present had even more to cheer about when Hall was harshly adjudged to have handled in the box and McCarthy stepped up to nonchalantly stroke home the resulting penalty.
The defeat leaves Wigan 17th, just one place above the Premiership drop zone.
Wigan boss Paul Jewell:
"The way we defended in the second half was shambolic really. People have jobs and responsibilities but at the moment they aren't doing it.
"It's not like us, but at this moment in time we're a little bit milky.
"People are saying we need a striker and we're looking for one, but you can't score four goals every game. We have to start defending properly."
Blackburn manager Mark Hughes:
"We have had a really good return from Christmas and can approach the new year with lots of optimism.
"We hope out current good form will end the same way it did last season, with us qualifying for European competition.
"We've had lots of injuries and players have been adapting to the Premiership, but we're improving all the time now."
Wigan: Kirkland, Boyce, Hall, De Zeeuw, Baines, Cotterill, Skoko (Wright 46), Landzaat, Kilbane, Heskey, Johansson.
Subs Not Used: Pollitt, Jackson, Teale, Cywka.
Blackburn: Friedel, Emerton, Henchoz (Todd 73), Khizanishvili, Neill, Bentley, Savage, Mokoena, Pedersen, Nonda (Derbyshire 46), McCarthy (Gallagher 77).
Subs Not Used: Brown, Kerimoglu.
Booked: Mokoena, Neill, Henchoz, Khizanishvili, Bentley.
Goals: Heskey 37 og, Derbyshire 58, McCarthy 76 pen.
Ref: M Clattenburg (Co Durham).