Third-placed Carmarthen Quins won 35-10 at Bonymaen on Wednesday and they start favourites to win at Glamorgan Wanderers, who have lost their last five matches.
Cross Keys could close the door on several other clubs for the vital seventh promotion place if they defeat Beddau at Pandy Park, but Narberth are back in form, yet face a difficult match at the Dairy Field against Llanharan.
Llandovery are taking no prisoners after scoring 55 at Newbridge and then 76 at Tondu on Wednesday. They entertain Blackwood, who won 35-29 in a thriller at Rumney on Tuesday.
Bonymaen, with more than 15 players injured and four facing possible early retirements, have a problem in fielding a side at Tredegar, while bottom club Treorchy go to Tondu with some hope and Whitland take a four-match winning streak to Bedwas, who are the most-improved club in the division.
In Division Two, leaders Llangennech go to Llantrisant, while second-placed Carmarthen Athletic entertain Llantwit Fardre before going to UWIC on Monday afternoon. The students have no match on Saturday as the are the free club.
Bynmawr at home to Corus and Maesteg at Abercynon are both fighting for promotion places, while bottom club Hirwaun face a derby match at Merthyr.
Division 3 East will see some hard battles as Penygraig face Fleur de Lys and Ystrad Rhondda go to Builth Wells while 3 West will see an interesting battle at Cwmllynfell, where Cardigan are the visitors, as leaders Felinfoel sit it out.
Brecon are close to capturing 4 East, but face second-placed Treherbert in a key match and in 4 West
top clubs Pontyberem, Maesteg Quins and Bryncoch all face away matches - against Brynamman, Mumbles and Penclawdd respectively.
In 5 East, New Tredegar take a one-point lead over Newport Saracens to an away match at Brynithel, while the Sarries face a useful Barry side and in 5 West Llandeilo are at home to Fishguard as nearest rivals Hendy go to Pontarddulais and Trebanos are at home to Loughor.
The big game in 5 Central is at Banwen, where the leaders must fear visitors Taffs Well, who ended Nantymoel's 18-month unbeaten record last Saturday. Nantymoel will be desperate to win their match, away to Cefn Cribbwr.
The biggest game of the season in North Wales will see Nant Conwy entertain Llangefni in 5 North, but other clubs will be fighting to avoid relegation, as nine of the 12 sides are in the latter position.
Welshpool could jump into second place in 6 North if they defeat Bro Ffestiniog at home.
There will be only rearranged matches in Divisions 6 and 7 and in 6 Central champions Abercwmboi travel for a hard match at Abercrave, while 6 East should see Fairwater as clear leaders if they win at home to Nantyglo.
The matches in 6 West will not affect promotion, but in 7 West Cefneithin go to Llanybydder, while Pontardawe and Pontyates face an interesting tussle.
Tonna face their last match - away to Gwernyfed - in 7 Central and in 7 East both Bettws and Llandaff North should record home wins over Blaenavon and St Alban's respectively.