Leinster's loss to Connacht and Ulster's victory over Munster last weekend has left Conference A of the Guinness Pro14 shaping up intriguingly.
With just one place up for grabs to book a spot in the competition's decider, Ulster are now in pole position ahead of this Saturday's head-to-head between the conference's top two at the RDS.
But Bernard Jackman expects Leinster to bounce back and maintain their hopes of retaining their title.
While he has been impressed by Ulster's recent form, "the question marks are still around their tight five" he told the RTÉ Rugby Podcast.
"I think that's where Leinster will go after them," he said.
"I expect a massive backlash from Leinster. It was the perfect storm for Connacht in that Leinster were maybe a little bit complacent, a little match shy.
"They're so good at getting their match-week right, no matter who plays, but obviously with the Covid problems against Munster, they had a very disruptive training time and they just looked completely out of sync - Johnny [Sexton] going off etc - but strengthen up that team a little bit, which they will and have guys back, and a bit of an edge mentally and I think they'll definitely fire."
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Leinster do have two games in hand on Ulster but one of those will be an inter-pro derby with Munster and the timing of the rescheduling makes it tricky for the reigning champions according to Jackman.
"But the reality now is that one of Leinster's games in hand is they have to go to Munster," he continued.
"I think that's probably going to be during the Six Nations so that's not a given. They have to go to Ravenhill in Round 16.
"I think theoretically, if Ulster could stop Leinster getting a bonus point and maybe get one themselves, they would be a in a really strong position.
"Realistically the best chance to beat Leinster in this competition is to keep them out of the final. If Leinster got to the final, you'd fancy them to get the win, so it's all opened up massively.
"It's good for the league. The league had become pretty monotonous with Munster having qualified after seven games and Leinster and Ulster after seven or eight games in the old format. But we know the new format is more refined with just the top team [in each conference], so I'm excited to see this game."
Follow Leinster v Ulster (7.35pm Friday) and Connacht v Munster (7.35pm Saturday) via our live blogs on RTÉ.ie/sport and the RTÉ News app or listen to live commentary on RTÉ Radio 1 Extra and RTÉ Radio 1.
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