All four provinces have named their teams for the upcoming derbies and it's momentous for Andrew Trimble
As he seeks a first win in six games, Munster head coach Anthony Foley has made seven changes to his side for Saturday's trip to Ulster.
In the back row, Tommy O'Donnell makes his first start since his return from injury, with Robin Copeland dropping to the bench.
Props Dave Kilcoyne and BJ Botha come into the front row, while behind them Mark Chisholm replaces Donnacha Ryan.
On the wings, Lucas Amorosino and Ronan O'Mahony come in for Simon Zebo and the injured Keith Earls.
Ian Keatley returns at out-half, with Tyler Bleyendaal dropping to the bench.
Andrew Trimble will earn his 200th Ulster cap on Saturday, which is a provincial record, when he lines out on the wing against Munster.
Captain Rory Best returns at hooker, while the other change in the front row sees Kyle McCall replace Andrew Warwick.
Lewis Stevenson comes into the second row for Alan O'Connor, while Chris Henry has shaken off a shoulder injury to come in at openside.
Connacht's Matt Healy has signed a new two-year deal with the province.
The winger-come-scrum half will remain west of the Shannon until at least the summer of 2018.
Since joining from Lansdowne in 2012, Healy has scored 20 tries in 57 appearances.
Healy has been named in the Connacht side for tomorrow's meeting with Leinster at the RDS.
Pat Lam has made three changes, all in the pack, to the XV that started the Stephen's Day loss to Ulster.
Tom McCartney replaces Dave Heffernan at hooker, while Andrew Browne comes in for Ultan Dillane in the second row.
And Jake Heenan starts at openside in place of James Connolly.
Connacht's Matt Healy tackles Ulster's Andrew Trimble ©INPHO/Dan Sheridan
There is no place for Cian Healy in Leinster's matchday squad for tomorrow's game at the RDS.
The prop is awaiting the result of a second hearing after he was cited for a strike with the knee to Toulon hooker Guilhem Guirado.
After initially having a two-week ban overturned, Healy is facing a re-hearing on the original charge in front of a different judicial officer in London.
Leo Cullen has made a full eleven changes from the win over Munster.
In the forwards, only Jack McGrath and Devin Toner are retained, while Rhys Ruddock, Josh van der Flier and Jordi Murphy form a new back row.
Jonathan Sexton comes back at out-half in place of the Bordeaux-bound Ian Madigan.
Luke McGrath, Dave Kearney, Ben Te'o and Rob Kearney also start.