A sloppy Ireland put a poor first period behind them to emerge 28-17 winners over Argentina in an unconvincing warm-up to next week's meeting of the world's top two teams when the All Blacks visit Dublin.
Ireland were fortunate to edge an error-strewn first 40 minutes and trailed early in the second period before finding some much-needed composure to pull away from the dangerous Pumas.
The hosts' day, however, was marred by the news that flanker Sean O'Brien, forced off through injury, had broken his arm.
"It was a real test match, really arduous. They were hard at the back, hard off the ruck and hard off the line and really squeezed us," Ireland coach Joe Schmidt said.
"They put some great pressure on our line-out and we struggled, but we got into the game on the back of our scrum, which was very good.
"There's lots to work on. It's not as surprising as, I suppose, it would have been had we had a full preparation or we hadn't had late changes."
Nicolas Sanchez opened the scoring early on with a fine long-range penalty.
Held up on their first raid, Ireland destroyed the visitors' front five in the resulting scrum as halfback Kieran Marmion sniped over for the opening try.
A missed conversion from Sexton allowed Sanchez to restore the advantage two minutes later.
Argentina's Matias Orlando ghosted through midway through the half to set up Bautista Delguy for an easy finish in the corner.
A scrappy Ireland continued to struggle with the wet ball in hand but a dominant scrum again served up a try-scoring opportunity that was ruthlessly taken by centre Bundee Aki.
After Sanchez accepted another penalty shot from distance, Sexton nudged the hosts into a scarcely deserved lead.
Argentina retook the lead again through a Sanchez penalty after the break and it stayed that way until Sexton made it 18-17 close to the hour.
Ireland improved to look far more like the team that had won 15 of their past 16 tests, and a try from replacement halfback Luke McGrath, after a decisive lineout steal, gave them some breathing for the first time.
Meanwhile Wales coach Warren Gatland says the strength of their bench played a major role in the narrow 9-6 victory over Australia in Cardiff that provided a significant boost to his side ahead of next year's World Cup.
Wales, who will meet Australia in their pool in Japan, ended a 13-game losing streak against the southern hemisphere team in an error-strewn arm-wrestle.
The ability to bring in experience off the bench, like first-five Dan Biggar and wing Liam Williams, gave Wales the impetus they needed in the closing stages, according to Gatland.
"I said that was the strongest bench we've put out in my time in Wales," Gatland told reporters.
"I thought the bench was outstanding. (Flanker) Ellis Jenkins was outstanding. (Lock) Cory Hill and the two front rowers came on and did well. Dan had to come out and kick a pressure kick."
Neither side created anything in the way of try-scoring opportunities as both defences stood firm. Unforced errors played a role too, as did the slow ball at the breakdown.
"The breakdown was tough for both teams. In the first half, we weren't dominant enough in the collisions," Gatland said.
"The boys dug deep. From a defensive point of view, that was probably the most comfortable we've been against Australia."
Wales' victory might have been more comfortable had fullback Leigh Halfpenny, usually so dependable from the kicking tee, not missed two simple penalty opportunities, one from directly in front of the posts.
"I never thought I'd see the day Leigh missed two easy kicks," Gatland said. "The pleasing aspect was that it didn't affect his game and he came out in the second half and performed really well."
Gatland also praised the decision to play Scotland as their opening November international opponents last weekend, which culminated in a 21-10 victory that gave them momentum going into the clash with Australia.
"The game last week was important for us. We probably wouldn't have won today had it been first up.
"We've got good momentum at the moment. Seven wins in a row. It puts pressure on those taking the field. We're in a really good place and looking forward to the World Cup next year."
Next up for Wales is a meeting with Tonga. Gatland suggested he might field a new team with a clash against South Africa to come the following weekend.
"That's down to the depth we've built," he said. "In the past, we've made lots of changes and the performance hasn't always been good. But we have depth now and I'm confident we'll put in a good performance."