Johnny Sexton is in line for his season's bow in Leinster's trip to Ulster on Friday night.
The 37-year-old is in the selection mix after having to bide his time over the first two weeks of the URC season.
And he could make an instant reunion with his Ireland half-back partner Jamison Gibson-Park, who was due to play in last Friday's home victory over Benetton before sickness ruled him out.
READ MORE: Leinster 42-10 Benetton: Dan Sheehan runs in FOUR tries during home opener
Another pair of Ireland's heroes from the New Zealand tour series win could also feature for the first time in this campaign.
James Ryan was also pencilled in to face Benetton, only to feel his hamstring during the Captain's Run and he was withdrawn as a precaution, while Tadhg Furlong is also available.
James Lowe and Hugo Keenan, meanwhile, remain sidelined through injury, while Ciarán Frawley, who was supposed to travel to South Africa for the Emerging Ireland tour after starting at out-half in last Friday's victory over Benetton, is out of that trip after picking up a shoulder injury late in the first half.
After a pair of opening wins against Italian opposition, the Blues are up and running against the backdrop of strong speculation that influential senior coach Stuart Lancaster has agreed to join Racing 92 in the summer.
Lancaster is scheduled for media duties this afternoon and it is possible that confirmation of the move will come before that.
Head coach Cullen is staying focused on team affairs and he predicts the Ulster clash will demand a step up in class from Leinster.
"Definitely," he said. "I think there's a great rivalry there always, there has always been.
"The derby games, that's what you want - you want the players battling it out against each other.
"It's an unusual start to the season when you think some guys haven't got up and running at all yet in our squad and in round three we're into a big derby game away from home, so it's a great challenge.
"Benetton do present a good physical test for you, at times there we got turned over at the ruck- that's where we lose our way.
"And Ulster will be strong in that area - they're strong in the contact area and they talk about it a lot themselves, they clearly place a lot of emphasis on it.
"How we are in that facet of the game will clearly have a large bearing on the outcome.
"It's a good early contest for us, both teams will be missing a couple of players who are travelling away so how that affects it, we'll wait and see."
Ulster will approach the fixture in confident mood having beaten Leinster twice last season.
Cullen admits that adds an edge to proceedings.
"Any time we lose it tends to sting, yeah," he said.
"That's because it means a lot to lads. When you're involved in the team and are wearing the jersey, it means a lot.
"So yeah, when you lose, particularly the derby games...it's slightly unusual, the timings of some of those games last year.
"But we lost them both so I wouldn't make any excuses really.
"Both teams were affected at different stages of the season, that's why I say it's unusual, straight into such a big game.
"But it's great to focus the minds as well and it's important for our guys in many cases to recover after the first game of the season.
"Maybe the fact that it was a Friday game and they can rest up over the weekend and then get back into action on Monday, recovering over the weekend is probably the big thing."
READ NEXT:
Martin O'Neill AND Liam Brady both praise Ireland display despite defeat in Scotland
Sanita Puspure and Zoe Hyde battle to win bronze at World Rowing Championships
Stephen Kenny rues fine margins as Ireland come undone at raucous Hampden Park
Amanda Serrano calls for Katie Taylor rematch after comeback victory
Boxing set to be scrapped from Olympics after 2024 following crucial vote
Get the latest sports headlines straight to your inbox by signing up for free email alerts
