By Tadhg Peavoy

Leinster have been beaten back-to-back coming into this one, and while it will be worrying for their setup, it is far too early for alarm bells to be going off.

Their 18-9 defeat to Northampton Saints came against a side who were absolutely determined to avenge their hammering to Leinster the week before, and the defensive effort the English side put in was superhuman.

While last Friday’s 11-6 defeat to Edinburgh was a game Leinster could, and probably should, have won. They were pummelling Edinburgh’s line at the death – like they were against Saints – yet lacked the finesse to get over in the final throes.

By contrast, Ulster are flying. Two facile Treviso wins and a well-earned home victory over Zebre have them in fine form, scoring tries for fun, and playing superbly confident rugby.

With five wins on the trot, they will come to the RDS in the best possible condition, and bristling with arrogance. They can back that up knowing they won in Dublin last term in the regular season on a 22-18 scoreline.

However, Leinster then came out on top of their provincial rivals in the PRO12 final at the same venue by 24-18.

Go back three games and Ulster were the victors in Ravenhill by 27-19. What’s the pattern: close matches. Margins of victory by six, four and eight are the surest indication of how close these sides are in terms of ability.

When they met in the final of the Heineken Cup at Twickenham in 2012, Joe Schmidt’s Leinster swatted Ulster away like an annoying little child tugging at an adult’s shorts during a club father-and-son match, smashing them 42-14.

But much has changed in the last year and a half. Ulster have closed the gap and matches between the side are highly unlikely to have 28-point spreads.

Leinster have no Jonathan Sexton or Isa Nacewa to spark brilliance in the backline, and both of those players are being missed sorely when it comes to one-score games for the Dublin team.

Furthermore, Brad Thorn’s presence and experience in the second row in that final cannot be underestimated.

Add to that the missing dynamism of Richardt Strauss at hooker and Leinster are missing a fourth player who elevates the team’s game to a higher level.

This Leinster side are one still in development. And the squad selection today shows that. Zane Kirchner has not yet displayed that he can deliver the accuracy and brilliance of Nacewa. He will get another chance from fullback today.

Zane Kirchner

Jimmy Gopperth has been steady at outhalf. He lacks Sexton’s creativity, but has arguably been the buy of the season in the PRO12 and his ability to do the right thing at the right time is invaluable.

Jimmy Gopperth

Those players are surrounded by developing talent in the form of Dave Kearney, Brendan Macken and Noel Reid, and a phoenix from the flames in the form of Luke Fitzgerald.

Kirchner and Gopperth must guide them through a tough derby encounter, because Ulster’s back line is littered with strength. Andrew Trimble, Luke Marshall, Craig Gilroy, Paddy Jackson and Paul Marshall all start.

The match-ups across the line are intriguing and there will be very little space for creation out there, especially if the underfoot retains the damp of the storm that has passed through these parts over the last few days.

In true clichéd fashion, the game will likely be won up front. The platform from breakdown and set-piece will be crucial and it is here I would worry for Leinster.

Against Edinburgh they were probably two men short of the experience they needed to grind out a win in atrocious conditions. This week, only Mike McCarthy and Sean O’Brien could really be called first teamers in the pack, with Rhys Ruddock not far off.

Sean O'Brien starts at openside flanker

However, Ulster’s pack is strong. Declan Fitzpatrick, Lewis Stevenson, Dan Tuohy and Roger Wilson all start. If they can stick it to the Leinster pack early on and get a lead of eight points, the pressure will be on Leinster as the threat of three defeats in-a-row looms large.

Dan Tuohy starts in the second row for Ulster

By contrast, if Leinster gain parity up front and come out of the blocks fiercely - like they did against Saints at Franklin’s Gardens - they will be hard to stop.

Both benches have game-breakers. Dominic Ryan, Luke McGrath and Ian Madigan for Leinster. Ruan Pienaar and Jared Payne for Ulster. So there are potential match-winning try scorers on both sides.

Like yesterday’s inter-pro between Munster and Connacht it will be close, and could in truth go either way. However, maybe this time an upset might be on the cards.

Verdict: Ulster to win by three.

Follow Tadhg Peavoy on Twitter here: @TPeavoy

Leinster XV: 15 Zane Kichner 14 Dave Kearney 13 Brendan Macken 12 Noel Reid 11 Luke Fitzgerald 10 Jimmy Gopperth 9 Isaac Boss 1 Michael Bent 2 Aaron Dundon 3 Martin Moore 4 Leo Cullen (captain) 5 Mike McCarthy 6 Rhys Ruddock 7 Sean O'Brien 8 Jordi Murphy.

Replacements: 16 James Tracy 17 Mike Ross 18 Jack O'Connell 19 Tom Denton 20 Dominic Ryan 21 Luke McGrath 22 Ian Madigan 23 Darragh Fanning.

Ulster XV: 15 Ricky Andrew 14 Andrew Trimble 13 Darren Cave 12 Luke Marshall 11 Craig Gilroy 10 Paddy Jackson 9 Paul Marshall 1 Callum Black 2 Rob Herring 3 Declan Fitzpatrick 4 Lewis Stevenson 5 Dan Tuohy 6 Robbie Diack (captain) 7 Sean Doyle 8 Roger Wilson.

Replacements: 16 Niall Annett 17 Tom Court 18 Ricky Lutton 19 Neil McComb 20 Mike McComish 21 Ruan Pienaar 22 Jared Payne 23 Michael Allen.

Referee: John Lacey (IRFU, 32nd competition game).
Assistant referees: Peter Fitzgibbon, Eddie Hagan-O'Connell (both IRFU).
Citing commissioner: Eugene Ryan (IRFU).
TMO: Sean Flannery (IRFU).