Verplank, the first Ryder Cup rookie to make the squad as a captain's pick, entered the World Top-20 on the strength of his fourth PGA Tour win, his first since last year's Reno-Tahoe Open.
There was no movement in the 14 spots that preceded Verplank.
Top-ranked Tiger Woods, a first-round leader at Royal Montreal this past week, faded after a three-over-par 73 in the second round. He'll look to get back on track this week in St. Louis, where the top players in the world will compete for the title at the American Express Championship, the third of four World Golf Championships events on the schedule this season.
Woods captured the last WGC title -- the NEC Invitational -- after an epic seven-hole playoff with Jim Furyk at Firestone last month. A victory at the American Express tournament this week would give Woods his fifth win in eight starts in the WGC individual events.
Woods and David Duval teamed up to win the WGC-EMC World Cup for the U.S. last December in Argentina.
Phil Mickelson remained No. 2 in the world, followed by Duval, Ernie Els, Vijay Singh, Davis Love III and Sergio Garcia. Northern Ireland's Darren Clarke stayed in eighth place, while PGA Championship winner David Toms and Scotland's Colin Montgomerie rounded out the top-10.
Furyk, Scott Hoch, Padraig Harrington of Ireland and U.S. Open champ Retief Goosen of South Africa held the next four spots, followed by No. 15 Verplank.
In order to accommodate the addition of Verplank to the top-20, Paul Azinger, England's Lee Westwood, Mike Weir and Mark Calcavecchia each dropped one place, and now occupy the 16th, 17th, 18th and 19th spots, respectively.
Weir, who followed up a missed cut with a tie for 34th during the PGA Tour's recently completed two-event swing through his home country of Canada, won last year's American Express Championship at Valderrama in Spain and will be on hand to defend his title this week at Bellerive Country Club.
Holding on to 20th place was Denmark's Thomas Bjorn, who was forced to withdraw after two rounds of last week's European Masters in Switzerland because of a shoulder injury.
Although Bjorn pulled out of the American Express event, his injury is not considered serious enough to keep him from competing for the European team at the Ryder Cup in England later this month.