Sheffield Wednesday's play-off push suffered a damaging blow following a 5-0 thrashing home to Blackburn.
Wednesday boss Garry Monk named an unchanged starting line-up from the 2-0 away win against Leeds.
Neither side really took charge of what was a very quiet first 15 minutes. Gallagher, who looked lively, created a slight opening threading Rothwell through whose cut back was cleared away by the Wednesday defence.
But Adam Armstrong soon created the opening for Blackburn 19 minutes in. His work down the left created space for a shot which was parried back to him by Dawson. Armstrong then found an unmarked Holtby who neatly slotted past Dawson.
Wednesday's poor start then got worse when Luongo saw red following a high challenge on Lewis Travis just four minutes after the opener.
Blackburn were dominating and deepened 10-man Wednesday's first half nightmare by doubling their lead in the 36th minute.
Travis' shot was brilliantly tipped onto the post by Dawson before the ball ricocheted off the woodwork, back off the goalkeeper and into the net.
Wednesday's collapse was punished further with Holtby's second of the game just before the break. He got on the end of another Armstrong cross to tap home from close range.
It was more of the same in the second half as Armstrong once again weaved his way through on the left before his cross was nearly turned in by Adam Reach who forced a quick-reaction save from his own keeper.
Blackburn's dominant afternoon continued when Lenihan added a fourth, three minutes after the break.
Stewart Downing received a short corner before his left-footed cross found Lenihan at the far post who guided his volley into the roof of the net.
The Owls then had one of their very few shots in the game when substitute Sam Hutchinson curled a shot just wide of the post from outside the box.
Blackburn could have had more but for Dawson's intervention keeping out Gallagher and Armstrong's efforts.
Gallagher grabbed the fifth for Blackburn in stoppage time, racing through on goal before smashing past Dawson.