Jennings admits to having mixed feelings when he watched David Wallace being carried from the pitch with a serious knee injury against England last weekend.
An innocuous tackle ended Wallace's hopes of participation in the World Cup and offered Jennings a tantalising glimpse of the number seven jersey.
Ireland open their tournament against the United States on September 11 and the 30-year-old Leinster back row is eager to be included in the starting XV.
"It's been a strange few days. On Saturday I was watching the game and when David went down I didn't know what to think," he said.
"Initially your thoughts go out to him because it was a bad bang he took, but I knew I was on the standby list. Sport can be very cruel sometimes.
"On Friday night I was playing for Leinster and was focused on them. Then you see what happens....
"David was a big part of the squad and is going to be missed, but now that I have the chance I'm going to make the most of it.
"I'm here to get the number seven jersey. We need all 30 lads competing for the spots. If we have fellas who aren't pushing we won't benefit."
With Wallace out of contention, coach Declan Kidney must re-examine the make up of his back row.
The return of Stephen Ferris from a serious knee injury was one of the few highlights of last month's warm-up internationals and the powerful Ulsterman could slot in at blindside with Sean O'Brien - should he recover from his own knee problem - moving to openside.
But European player of the year O'Brien is Ireland's most dangerous operator on current form and Kidney will be anxious to avoid the potential danger of diminishing the threat he poses by tinkering with his position.
Denis Leamy can play across the back row but is least comfortable at openside.
The squad's only specialist seven is Jennings and his work on the ball and support play may yet appeal to Kidney on the grounds his presence offers greater balance.
"I'm certainly not a ball-carrier like David or Sean O'Brien. I try to get as much ball as possible and link up," said Jennings.
"I'm a different player to the other guys in the back row."
After four successive defeats in the build-up the World Cup, Ireland need a statement of intent against the USA, who are now coached by Kidney's predecessor as Ireland coach, Eddie O'Sullivan.
The losses to Scotland, France home and away and England have been heavily scrutinised, but Jennings insists they have little relevance to what happens in New Zealand.
"We had a meeting on Tuesday before we set off for New Zealand and there was a buzz around the room," he said.
"Unfortunately results haven't gone our way. We have to accept that and work on those things.
"It's just a matter of putting that behind us now. We are here to do a job.
"Pre-season games only account for so much. It's all about how we perform in the World Cup and that starts against the Americans."
Ireland are based in Queenstown, the adventure sports capital of New Zealand, for the first week before heading to New Plymouth to face the USA.
The squad have enjoyed the spectacular scenery of Queenstown from the moment they were welcomed at the airport by over 500 supporters. Jennings intends making the most of his time here.
"It was a long journey over here and we were very tired getting off the plane, but we got a lift when we saw all of the kids there to greet us," he said.
"There were a lot of Irish flags and it was an unbelievable welcome.
"It's a beautiful place, I've never been somewhere like this before. I'm going to enjoy it.
"There's an important balance to strike between concentrating on rugby and enjoying ourselves off the pitch.
"We need to work when we are in the gym or on the training field, but we can't be here for so long and not enjoy our surroundings."
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