Time is almost up for the Yorkshire club, whose return to National League One would be confirmed if Worcester collect two points at Wasps on Saturday and Leeds finish without a point against title play-off contenders Harlequins on Sunday.
With Wasps expected to beat an injury-hit Worcester side though, Leeds' fate will probably be delayed until next weekend when they visit Premiership leaders Gloucester.
Leeds have recorded just two wins in 18 league starts this term, while their last Premiership outing produced a 66-7 defeat against Heineken Cup semi-finalists Saracens.
And it did not get any better in Europe seven days ago, as Bath inflicted a 57-5 drubbing on Lancaster's men.
He said: "We have obviously struggled with injuries and form, coming up against two sides playing at the top of their game.
"As a consequence, it is nice to come back home, and we have spoken as a group about the need to put in a quality performance in front of our own fans.
"The players recognise the need to remain truly competitive in these last four league games.
"There are too many people who have worked too hard to allow the season to drift, when we have so much to build for in terms of next season and the overall evolution and growth of the team."
Lancaster has made nine changes following the Bath game, with centre Andy Tuilagi, fly-half Alberto Di Bernardo and scrum-half Joe Bedford among several players who return to the starting line-up.
England wing David Strettle, meanwhile, could return from a foot injury that ended his RBS 6 Nations campaign in the opening game against Wales on February 2.
Strettle is on the Harlequins bench at Headingley Carnegie, where he is joined by Test colleagues Andy Gomarsall and Nick Easter.
European Cup semi-finalists London Irish visit Newcastle on Sunday, with qualification for next season's showpiece European event high on their agenda.
Irish, unless they win the tournament this term, are likely to need a top-six Premiership finish to confirm their place in 2008/2009.
The Exiles currently lie eighth, five points behind sixth-placed Saracens.
Rugby director Brian Smith said: "With four Premiership games to play, we believe we can secure a sufficiently high league position to be among the qualifiers.
"Sunday's game is very important if we are to succeed in reaching our objective."
Injury rules out fly-half Mike Catt for Irish's trip to Kingston Park, so Eoghan Hickey deputises, with Shane Geraghty featuring at inside centre.
Newcastle boss Steve Bates has made four changes from the side that beat Challenge Cup quarter-final opponents Castres last Saturday.
Flanker Ben Woods suffered a fractured hand during that game, so he is replaced by Brent Wilson, while Tom Dillon takes over from ankle injury victim Jamie Noon in midfield and there are also starts for prop David Wilson and hooker Andy Long.