By Brendan Cole

Leinster v Ulster, RDS, 7pm. 

The fairytale script for this one might see one Brian O’Driscoll carving a line through the centres before getting in under the sticks for a vital try some time in the last 10 minutes.

Ulster, who have been authors of their own downfall on a couple of occasions in recent weeks, do not look like they are in the form to play along with that particular script.

The visitors’ pack looks particularly well suited to party-pooping against a Leinster outfit that is not strong enough in the pack win an arm-wrestle, even if the likes of Shane Jennings, Rhys Ruddock, and Sean Cronin play to the top of their form.

If back-injury victim John Afoa were present, Ulster might even have been fancied to get a decisive edge.

Both sides can expect a good supply of lineout ball with Devin Toner and Cronin capable of working tandem in the friendly surrounds of the RDS while Ulster, unless Rory Best has one of his rare off-days, also look capable of looking after their own ball out of touch.

Afoa’s absence means the Ulster scrum is weakened but Best is rarely part of a beaten of a beaten front row and should be able to manage that situation too.

That pattern of tit-for-tat may well be repeated in the close-in ball-carrying exchanges, with neither side having a clear edge on the personnel front.

Leinster might be just ahead with Cian Healy and Jamie Heaslip, but Ulster’s outstanding tackling has been one of the hallmarks of Mark Anscombe’s reign and – assuming they can all stay on the pitch – should good enough to keep a lid on Leinster.   

If that scenario does play out, chances to shine for what are two high-class sets of outside backs will be limited.

That could mean that, as is often the case in knockout rugby, it will come down to the half-backs and in that area Ulster have an obvious advantage with Ruan Pienaar in the starting line-up.

The South African is a peerless organiser, capable of generating forward flow and width as required with ball in hand and with a magnificent kicking game to boot.

Pienaar’s vision and accuracy in combination with their strong tackling and turnover capability could just give Ulster a chance to land some blows on the counter.

If he can link up with Jared Payne and co out wide – and it is interesting that a second ‘outside centre’ has been deployed at 12 in the shape of Darren Cave – things will get interesting for the travelling support.

Leinster do have the advantage on the bench, where Jack McGrath, Mike Ross and Sean O’Brien are capable of exerting an influence in key areas in the second half if at their best, while Ian Madigan could also be important as the game cuts up in the final 20 minutes.

Leinster are unbeaten at the RDS in the Rabo Pro12 this season but have been distinctly unimpressive in big games this season.

A scenario in which Ulster edge ahead through the first hour only to get overhauled in the final quarter – perhaps with a final flourish from Leinster’s number thirteen – is not hard to imagine.

But if Pienaar stays on the pitch for the 80 minutes, you could also see Ulster just hanging on, and ending Ireland’s greatest player’s career a week earlier than most would like.

Prediction: Leinster 19-22 Ulster

Leinster: R Kearney, F McFadden, B O'Driscoll, G D'Arcy, D Kearney, J Gopperth, E Reddan, C Healy, S Cronin, M Moore, D Toner, Q Roux, R Ruddock, S Jennings, J Heaslip (capt).

Replacements: A Dundon, J McGrath, M Ross, L Cullen, S O'Brien, I Boss, I Madigan, Z Kirchner.

Ulster: C Gilroy, T Bowe, J Payne, D Cave, A Trimble, P Jackson, R Pienaar, C Black, R Best, R Lutton, J Muller (capt), I Henderson, R Diack, C Henry, R Wilson.

Replacements: R Herring, A Warwick, A Macklin, D Tuohy, S Doyle, P Marshall, J McKinney, L Marshall.

Watch Leinster v Ulster RaboDirect PRO12 semi-final live on RTÉ Two and RTÉ.ie/sport from 6.30pm (kick-off 7pm) on Saturday 17 May