Brian McCaul scored twice as Linfield completed their third emphatic league win over Donegal Celtic this season.
Linfield took an early lead when Philip Lowry stabbed in after John Connolly had failed to gather a corner.
McCaul netted a penalty early in the second half after Pearse Devine had fouled Michael Carvill and then Matthew Tipton made it 3-0 with a fine chip.
McCaul got Linfield's fourth, Devine was sent-off for a second yellow and Mark Miskimmin got a late DC goal.
The win leaves the champions four points behind second-placed Crusaders and 13 behind runaway Premiership leaders Cliftonville.
It was Linfield's fifth win in a row in the league and they are unbeaten in their 11 Premiership matches since losing 3-0 away to Cliftonville on 10 November.
Earlier in the season Linfield had beaten Donegal Celtic 4-0 and 3-0.
Donegal Celtic who have lost five in a row in the league, remain one from bottom and four points ahead of basement club Lisburn Distillery.
It was a blustery night and that may have contributed to Lowry's opener which came in the second minute.
Michael Carvill's corner put keeper Connolly under pressure and Lowry pounced to score his first goal of the season.
Donegal Celtic thought they had equalised early in the second half when Paul Bradley forced the ball in after a Ciaran Gargan corner, but referee Arnold Hunter blew for a foul on Linfield keeper Ross Glendinning.
Linfield went two up through McCaul's penalty after the foul which earned Devine his first booking.
Tipton then scored with a brilliant chip over Connolly from the corner of the penalty area and Lowry's through ball sent McCaul in to beat Connolly for 4-0.
Devine got his red card for a foul on Jamie Mulgrew but DC had the last word when former Blues forward Miskimmin pounced on a mistake by skipper William Murphy.
"I thought we played tremendously well in the second half and scored some good goals," said Blues manager David Jeffrey.
"Matthew Tipton's goal was worth the admission money alone."