Sheffield United's Gus Hamer scored the Blades' opener
Sheffield United opened up a three-point gap over Leeds at the top of the Championship after beating Wayne Rooney's struggling Plymouth at Bramall Lane.
Chris Wilder's side had been given a helping hand by ex-Blades boss Paul Heckingbottom, whose Preston held Leeds to a draw at Deepdale earlier on Saturday.
And despite a largely unconvincing display, a first-half strike from Gus Hamer and a late penalty converted by Kieffer Moore proved enough to secure the victory.
No-one has scored against the Blades at Bramall Lane since Lyndon Dykes for QPR on 17 August as the South Yorkshire side have now won nine home games in a row without conceding.
Plymouth remain without a win on the road in 11 games and stay just a point above the bottom of the table in 23rd place.
Despite this being one of the Blades' least convincing performances victory further embellished their outstanding home record this campaign.
It also extended their unbeaten run to 10 matches stretching back to a 1-0 defeat at the hands of Middlesbrough on 23 October.
It was to Plymouth's credit that despite an early blow through Hamer's peach of a half volley from the edge of the box, they never gave up trying to find a way back into the game.
Rami Al Hajj, Darko Gyabi and Mustapha Bundu all found ex-Plymouth keeper Michael Cooper in fine form during a first half in which the visitors carved out more openings than the league leaders.
Wilder had looked less than happy as he paced from the dugout at half-time but they showed no discernible improvement early in the second half.
It led to the hosts making a triple change 10 minutes into it with Sam McCallum, Moore and Jamie Shackleton introduced.
But it was Lewis Gibson who went closest to equalising when he hit the post with a header on 55 minutes before Bundu, Al Hajj and Ryan Hardie were again denied by Cooper.
It took a penalty two minutes from time, converted by Moore after Tom Davies was felled by Brendon Galloway, to finally remove hope from the visitors.
Sheffield United manager Chris Wilder told BBC Radio Sheffield:
"It was a hard watch for me and I imagine it was a hard watch for everybody else. But we took the big moments but they were better than us in the first half.
"It shows the intensity of Championship football and how demanding it is especially off the back of Sunday afternoon, Wednesday night and coming back in getting a quick turnaround to Saturday.
"Three games in six days is punishing the teams at the top of the division. I don't get it. We've not got the biggest of squads and we are stretched a bit at the moment.
"There was a lack of energy on the pitch in the first half and they were the better team first half so we were delighted to get that second goal and calm everybody down. We go on yet again preserving an incredible home record that will now go past Christmas Day."
Plymouth boss Wayne Rooney told BBC Radio Devon:
"We are disappointed with the result and I didn't feel we deserved to lose the game, but that's what Sheffield United are - a very efficient team who are good in both boxes and that's what they did again today.
"I thought a lot of our play was good and the lads put a shift in but we missed opportunities. Performance-wise good but the result was disappointing.
"It was a better performance and I think everyone could see that. There was a very good reaction to going a goal down and then I felt as the game was going on I felt we could get something out of it.
"It opened up a little bit towards the end, they get a penalty and the game was done.
"We had some good opportunities, half ones and [Lewis] Gibson hits the post so there are lots of positives from the game but disappointed with the result."
