Luke Fitzgerald believes that Leo Cullen is looking for the Leinster bench to propel the side into the Guinness Pro12 final, but doesn’t necessarily agree with the tactic.

Cullen has made three changes to the starting 15 that faced Ulster two weeks ago for Friday night’s clash (KO 7.45pm) with Scarlets at the RDS, with Jonathan Sexton, Robbie Henshaw and Ross Molony coming into the side.

It means a strong-looking replacements bench will be itching for action, particularly among the forwards where Cian Healy, Devin Toner, Dan Leavy and Seán O’Brien have been selected.

Speaking on the RTÉ Rugby Podcast, former Leinster and Ireland back Luke Fitzgerald says that holding game-changers in reserve is a tactic Cullen has implemented since taking over from Matt O’Connor.

"Leo’s a big man for having impact off the bench. I’d have the impact from the start."

"Myself and Leo differ slightly in some views," he said.

"He’s a big man for having impact off the bench. I’d have the impact from the start.

"I see that in different selections watching him as a coach and playing under him as well."

The exclusion of Toner has raised eyebrows, but the towering second row picked up a knock against Ulster, while O’Brien is still returning to full fitness after his latest hamstring setback.

"Devin would be calling the lineout normally, set-piece is huge," Fitzgerald added.

"He’s definitely a guy who must have picked up a knock, we have got to believe Leo in what he says there, and Seánie [O’Brien] is returning from injury, so there’s no point in reading too much into it.

Cullen has a vast array of options at his disposal with regards to personnel in the forward division, and has opted for just two backs for the semi-final, with Jamison Gibson-Park and Zane Kirchner primed for action if required.

"I can see why he [Cullen] is doing it, the ploy with six forwards, I just fee sometimes I would go with the impact straight away."

"You look at the Scarlets bench and they don’t have that impact that Leinster have"

Former Leinster, Connacht and Munster back James Downey believes that while Scarlets, who have won 10 of their last 11 league games, can put it up to the hosts, there is a significant difference between the sides on the sidelines.

"You look at the Scarlets bench and they don’t have that impact that Leinster have," he said.

"Coming at 60 minutes, you are fatigued and tired and you will have Seán coming on.

"It’s go out there, give it socks for 50 minutes and then we will make some changes with fresh blood."

Listen to live coverage of the Pro12 semi-final between Leinster and Scarlets on Friday (19.45pm) on Friday night's Game On on 2FM.

Live coverage of the second semi-final between Munster v Ospreys  (6.15pm) and Northampton v Connacht in the Champions Cup play-off (4pm) on Radio 1's Saturday Sport.