Johnson survived a late push by Spanish 21st seed Jon Rahm to win the 18-hole final at the tournament last year.
Justin Thomas can take the rankings top spot from Johnson with a tournament win, but will first need to get through a group that includes Luke List, who Thomas defeated in a playoff at the Honda Classic last month, Patton Kizzire and Francesco Molinari.
Japanese players Hideki Matsuyama and Yusaku Miyazato are in group five along with Patrick Cantlay and Cameron Smith.
Fresh off his win at Bay Hill, Rory McIlroy has been handed a favourable draw as part of a group that includes Brian Harman and Peter Uihlein, who will be making their Match Play debuts, and Texas native Jhonattan Vegas.
Defending Race to Dubai champion Tommy Fleetwood will square off against Daniel Berger, who has four top 14 finishes this year, and Kevin Chappell, who tied for seventh at Bay Hill.
The group also includes Ian Poulter and Fleetwood said he looks forward to doing battle against his fellow Englishman on Wednesday.
"He was described as a match play ninja and I've never really gone up against a ninja before in my life, so it will be a new experience," Fleetwood told reporters on Tuesday.
The tournament comes to Austin at a time when police are searching for suspects linked to five bomb attacks that have rocked Texas this month.
South African Dylan Frittelli said he had noticed increased security at the course on Monday.
"They had security officials on every corner of the clubhouse and on the exterior, as well," he told reporters.
"It was pretty tough to get through all the protocols," he said.
(Reporting by Rory Carroll in Los Angeles)
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