Leeds Carnegie and Rotherham Titans need three points from their last three games of the regular season to be mathematically certain of joining Bristol Rugby and London Welsh in the Greene King IPA Championship play-offs.
As things stand, Yorkshire rugby's flag-bearers are on 70 points – 13 ahead of fifth-placed London Scottish.
All three contenders are in action on Sunday with Rotherham having the toughest test on paper with a trip to Cornish Pirates.
The Titans have only ever won once in 11 attempts away to the Pirates, their last visit to the Mennaye Field ending in a 53-21 hammering in November 2012.
Leeds will be looking to make it two wins in nine days against Plymouth Albion at Headingley Carnegie following their British & Irish Cup quarter-final win over the same opposition last Friday.
Leeds have never lost at home to Albion at this level in league or cup.
London Scottish play host to ninth-placed Bedford Blues who could still move up two places or drop two places in the GKIPA table depending on how they and the sides closest to them fare in their remaining games.
Blues won 21-13 when the sides met at Goldington Road on New Year's Day.
To book tickets for Sunday’s clash, click here, as Scottish look to consolidate their fifth place position which would be their highest league finish in 15 years. Hospitality for this game is sold out.
The televised clash between Moseley and league leaders Bristol tops Saturday's triple bill, kick off at Billesley Common is 17:05pm.
Nicky Robinson and George Watkins both grabbed a brace of tries apiece in the first meeting of the season: a 29-8 win for Bristol at the Memorial Stadium on December 28.
Moseley can take comfort though from the fact they have never lost to Bristol at Billesley Common.
The league's bottom two clubs both feature in Saturday's earlier kick offs, with Jersey away to London Welsh and Ealing Trailfinders at home to Nottingham Rugby.
A win for Nottingham at Vallis Way would make them safe from the threat of relegation.
Green & Whites skipper Brent Wilson scored a hat-trick yet still finished on the losing side after Ealing pulled off a shock 28-27 win at Meadow Lane at the turn of the year.
Ealing need to win to maintain any realistic hopes of reeling in Jersey who have an eight-point cushion at the foot of the table.
Jersey lost 33-26 when they last played London Welsh.
Welsh have won their last six games and are currently four points behind leaders Bristol.
Round 21 fixtures
Saturday April 12
London Welsh v Jersey, KO 14:00
Ealing Trailfinders v Nottingham Rugby, KO 15:00
Moseley v Bristol Rugby, KO 17:05 (Live on Sky Sports HD)
Sunday April 13
London Scottish v Bedford Blues, KO 14:00– to book tickets, click here.
Cornish Pirates v Rotherham Titans, KO 15:00
Leeds Carnegie v Plymouth Albion, KO 15:00