Johnson's one-shot win came in his first start as world No. 1, and it strengthened his grip on the top spot over an idle Jason Day.
The man closest to Johnson in Mexico City was Tommy Fleetwood, who continues his rapid ascent through the rankings in 2017. Fleetwood won earlier this year in Abu Dhabi, and his WGC runner-up helped him move up to No. 35. It's 20 spots higher than last week and 64 spots higher than where he began the year.
Fellow Englishman Ross Fisher also made a move with a pair of important deadlines looming. Fisher's T-3 finish jumped him from No. 72 to No. 55, with the top 64 next week qualifying for the WGC-Dell Match Play Championship.
Fisher also now has a chance to crack the OWGR top 50 by March 27, a feat that would earn him his first trip to the Masters since 2012.
With his next start still up in the air because of lingering back issues, Tiger Woods fell two spots to No. 713.