Alan Quinlan believes the summer tour to Argentina is Darren Cave's last chance to stake a real claim to become Brian O'Driscoll's successor in the Ireland No 13 jersey.
Injury to Robbie Henshaw has cleared the way for the Ulster centre to audition for the role on the two-Test tour as he remains the only natural outside centre in the squad.
Joe Schmidt may still bring in a back-up player, with Quinlan calling for the inclusion of Leinster's Noel Reid or Ulster's Michael Allen, but cover for Cave is likely to be provided by Keith Earls or Fergus McFadden.
Cave's five caps so far have come on summer tours.
He complained last December that his "face doesn't fit" with Irish selectors.
However, the 27-year-old, who was part of the extended Six Nations squad, now has an opportunity to impress Schmidt in Argentina and Quinlan believes he won't get a better one.
"Yeah, it is," the former Munster flanker replied when asked is it now or never for Cave. "He's got to step up now and take hold.
"You can never say, but from my own experience, I was on the edge of the squad a good few times and you get opportunities and get injuries.
"Darren Cave has had a few setbacks with injuries and disappointments. It's a great opportunity for him. He's got to perform now, not just in the matches but in training, and be a leader and show Joe Schmidt.
"I'm a fan of quality training as well, and having a close look at guys and the little things that they can do in training sessions. So it's time for him and an opportunity if he gets to start. But he's got to show hunger to want that and deliver a performance. If he wants to play international rugby he's got to do something on this tour."
Schmidt's options at outside centre will broaden next season when Jared Payne qualifies through residency and Henshaw and Tommy Bowe return from injury.
O'Driscoll retires after tonight's Pro12 final as Leinster take on Glasgow, but Quinlan does not believe he will leave as big a void as once feared.
"I mean this respectfully to the guy, but I think over the last year he became more normal," he said.
"He wasn't hitting the same heights, making all of those clean line breaks and breaking the gainline all the time. I think he had to adapt and change his game, like a lot of players have to do in their 30s when they have lost that yard of pace maybe, especially for a back.
"So, yeah, preparation for life without Brian O'Driscoll started a year and a half ago even, maybe two years at Leinster."
Meanwhile, Matt O'Connor had the unenviable job of taking over from Schmidt when the hugely-popular and highly-acclaimed New Zealander succeeded Declan Kidney as Ireland's head coach last summer.
Leinster's Heineken Cup exit to Toulon at the quarter-final stage dashed O'Connor's hopes of success in Europe this season and although the Dublin-based province's 'A' team retained the British & Irish Cup by beating Leeds Carnegie in last weekend's final, toppling Glasgow tonight would mean much more to the Australian at the end of his first season in charge.
O'Connor has made three changes from the team which beat Ulster two weeks ago in the semi-final.
With Mike Ross returning at tight-head, Martin Moore drops to the bench. And lock Mike McCarthy's availability following injury sees him named alongside Devin Toner at the expense of Quinn Roux who has not made tonight's 23.
Winger Dave Kearney underwent surgery on an ACL knee injury yesterday and his place in the final has gone to Zane Kirchner who wears 11.
Other than that it's as you were for the holders, which means that, as in the semi-final against Ulster, Kiwi Jimmy Gopperth starts at 10.
* Donncha O'Callaghan will realise a childhood family dream when he makes his Barbarians debut against the England XV at Twickenham tomorrow.
The Munster and Ireland lock broke his 101 Greatest Tries video as a youngster, playing and replaying Gareth Edwards' classic 1973 Barbarians score against the All Blacks.
O'Callaghan's older brother Ultan won Barbarians selection to face the Combined Services in 2002, and now the British and Irish Lions second row admitted delight at following suit.
"We were a rugby-mad house growing up," said O'Callaghan.
"We had the 101 Greatest Tries video, and I remember after about three months you couldn't watch the 1973 try against New Zealand any more because the tape was so worn, from just rewinding over and over.
"Growing up with three older brothers, when we played rugby in the garden it was always the Baa-Baas versus Ireland, because no one ever wanted to be Scotland or England!
"Even back then you threw the ball around when you did it. I'm delighted: I was ready to swim over when I got the call."
* Jonny Wilkinson will be added to Toulon's coaching staff next season, after he brings the curtain down on an illustrious 17-year playing career this weekend, following Toulon's clash with Castres in the Top 14 play-off final.
But the French side's coach Bernard Laporte is keen to bring the 35-year-old World Cup winner Wilkinson onto his staff.