But Sexton's injury against England and Ireland coach Declan Kidney's decision to leave O'Gara out of the starting line-up against Scotland meant Jackson found himself in possession of the No.10 jersey for the games against Scotland, France and Italy.
The 21-year-old struggled against Scotland, missing three of four kicks before being replaced in the 12-8 defeat but fared better in the 13-13 draw with France at the Aviva Stadium.
And his final game of the Championship came in Rome will be one to forget for all of those in green as the class of 2013 became the first Irish side in Six Nations history to lose against Italy, going down 22-15.
"It's not great to be part of the first team to lose to Italy, so we're very disappointed. But Italy played well," Jackson told the Irish Times.
"The young guys are chuffed to have got our chances, but we haven't got a win yet. This has been the biggest learning period I've had in my career so far.
"The last three weeks have been up and down."
Ireland's RBS 6 Nations campaign has been heavily disrupted by injury and an already depleted starting XV in Rome was further weakened by injuries to Keith Earls, Luke Marshall and Luke Fitzgerald.
Further hindering Ireland's chances of avoiding a first RBS 6 Nations loss to Italy was the sin-binning of Brian O'Driscoll, Donnacha Ryan and Conor Murray and Jackson conceded it had been a very testing day at the office.
"The amount of guys we lost didn't help and Italy are a very strong team. The number of penalties we gave away killed us," he added.
"Those injuries were something I've never experienced before. I looked around and both Lukes were gone, Brian was in the bin and Pete O'Mahony was on the wing.
"I wanted to calm things down by kicking for territory but our kick-chase wasn't so strong. It was about striking a happy medium between keeping the ball and securing territory, but those penalties killed us."