Both sides, perennial challengers and serial winners of the competition, have looked impressive thus far in winning their first two fixtures, and picking up a bonus point each, to lead the table on nine points.
Shannon have played in fits and starts in their two wins to date, over Blackrock and Lansdowne, and will need to be tuned in for longer if they are to take the scalp of their neighbours. They have been 'doing enough' rather than dominating, but one can expect them to be more focussed on Sunday. Garryowen looked well-rounded against Galwegians, and Ray Niland, in particular, looks a threat with three tries already racked up in the league. Close, but it's hard to go against Shannon.
Elsewhere, UCD and Cork Constitution at Belfield looks the pick of the Saturday fixtures. UCD have looked very bright in beating Dungannon and Lansdowne. Their backs have been flowing freely and they have benefited from the release of a number of contracted players such as Brian O'Riordan, the Blaneys and James Norton. This one will test their mettle as challengers as Cork Con, having lost their opener to Buccs, rallied with a good 30-20 home win over Ballymena last week. The kicking of scrumhalf Pat McCarthy and finishing of winger Cronan Healy have been a feature for them.
The other fixtures offer an interesting mix. Ballymena will feel they should have more then their one point, particularly from their opener against Clontarf, and will be looking to take the points at home to Co. Carlow. The latter, though, were somewhat unfortunate to go down at home to Clontarf 11-6 last time out. Both need the points badly.
So too, do Lansdowne and Galwegians, who play at Lansdowne Road. Lansdowne improved last week, despite going down to Shannon, and may just have enough to get the win here, as 'Wegians didn't impress against Garryowen in going down 33-11.
Mid-table Buccaneers and Blackrock will both see this as a chance to launch themselves as challengers, and this is precisely the type of match you have to win to do so. If 'Rock are to win they will have to suppress the home crowd and the significant Buccs pack.
Clontarf, a point off the pace, take on Dungannon at Castle Avenue, in a match they will be favoured to win and keep pace with the winners of the Limerick derby. Dungannon were well beaten by UCD and were fortunate to gain an opening win away to Belfast Harlequins, so this looks a big ask for them.
Trinity face a challenging trip to Belfast Harlequins in a match switched to Friday evening (7.30). But they have adjusted well to life at the top so far, having drawn with Galwegians and secured a very creditable win over Buccs. Harlequins haven't delivered on their promise, and their backplay let them down in going down to Blackrock last time out.
In Division Two, Ballynahinch and Dolphin can maintain the pace at the top with home wins over a struggling Barnhall and a mid-table Old Crescent respectively. St. Mary's will be looking to keep up the pressure at home to a useful UCC side, as will Bective Rangers away to a porous-looking Old Belvedere. UL Bohemians and DLSP will be looking to put themselves in contention while delivering a blow to the other, while Terenure host Highfield, Thomond host Malone and Waterpark host Midleton.
In Division Three, leaders Corinthians are inactive, so there is a chance for both teams to take their claim when Connemara travel to an unbeaten Clonakilty. Equally, Sunday's Well will be eyeing up top spot when they travel to Old Wesley, as will City of Derry at home to Banbridge and Greystones away to Wanderers on Sunday. Ballina visit Portadown in a basement struggle, Queens host Ards, Instonians host Bruff and Skerries host neighbours Suttonians for local bragging rights.
This weekend will go some way to sorting the wheat from the chaff in all three divisions, so why not get out there and let out a roar or two?