The defending champion said he was relieved to beat the sticky Kevin Na with a par at the second hole of a Group 3 playoff after they halved their 18 hole match at Austin Country Club to finish with two and a half points each.
And while Johnson has been hugely impressive so far, beating Shane Lowry 4 and 3 for his third win in a row in Group 14, McIlroy’s power and his hot putter will be tough to counter even if the tight, firm course sets up better for the reigning Open champion.
“This is a golf course that sets up perfectly for Zach,” McIlroy said.
“It’s his sort of golf course. Very much have much a precision course and that’s his game. If he can get it in play, he’s going to be very tough to beat.
“I feel like I’m playing well. I’ve had some good battles with the team format with Zach over the years in the Ryder Cup, so tomorrow should be a good one.”
McIlroy had to battle hard to beat Na, who won the second with a par to McIlroy’s double bogey six and then birdied the fifth to go two up.
The world No 3 birdied the short seventh from eight feet and the ninth with a 68-foot bomb to get back to all square.
And while he lost the 10th to go one down again, McIlroy insisted that the longer a match goes on, the stronger he feels about his chances.
“Any time I go into the back nine, even today, I was down after 10 holes but I knew that I’d played the back nine well this week and I had done well,” he said.
“Any time the match goes the distance, I feel like I have a better chance. Thankfully, I was able to get it done again today.”
After another birdie two at the 11th levelled the match, McIlroy won the 15th in birdie to go one up but lost the 16th after a poor drive before earning his spot in the last 16 in sudden death.
“It is a sigh of relief, nice to get through and nice to be here for the weekend,” Mcilroy said after Na drove into trouble at the second and lost to a par four.
“My match play record has been pretty good over the last couple of years. It was nice to get another win and be here for the last 16.
“I have got a tough opponent in Zach Johnson tomorrow. I know I have to play very, very well. Just delighted to get through.”
The expected rematch between Paul Casey and Jason Day never happened with the Englishman, who like Graeme McDowell was already out of the tournament, forfeiting the match due to a stomach bug to send the Australian into the last 16.
McDowell, meanwhile, was down for most of the day to Thongchai Jaidee but halved in the end to finish the week with two halves and a defeat from three matches.
The play-off between McIlroy and Na followed one between South Africa’s Branden Grace and American Chris Kirk, who had to wait more than two hours for the first tee to clear after Grace thrashed Scotland’s Russell Knox 5&4 and Kirk defeated David Lingmerth 3&2.
A par on the first extra hole was then enough for Kirk to advance to face compatriot Bill Haas, who birdied the 17th and 18th to defeat in-form Australian Adam Scott.
Day will face Brandt Snedeker in the last 16 after Snedeker defeated Charl Schwartzel 5&3, while Matt Kuchar advanced to take on Brooks Koepka thanks to a 3&2 win over former US Open champion Justin Rose.