The world's top three battle it out in an enticing Bay Hill Invitational field in Orlando this week.
Having regained top spot, Tiger Woods bids for a fifth victory in six visits to the Florida course.
Els has been in excellent form on the Middle East stretch of the European Tour, winning both events in style.
Singh has won once in the US this season and missed a short putt to lose a play-off with Padraig Harrington at last week's Honda Classic.
Woods insists that the number one ranking is not a priority.
"It's not what drives me," he said. "I guess it might be more interesting for the fans but I'm not a fan, I'm a competitor.
"My whole idea is to win a tournament just like Vijay, Ernie and anybody else in the field."
Woods has shown some imperious form in his four strokeplay events so far this season, finishing joint third in his opening outing and winning twice, most recently overturning a two-shot final day deficit to defeat Phil Mickelson at Doral.
In addition to his four European events, Els, ranked third in the world, has played in three US events, and has yet to finish outside the top six on either tour.
World number two Singh surprisingly missed the cut at the Pebble Beach Pro-Am, but has four top-five placings from his seven strokeplay tournaments thus far.
Retief Goosen, ranked fifth in the world, also takes part this week, looking to build on his share of eighth place at Doral.
Woods, Goosen and Els form a formidable three-ball, teeing off at 0840 local time.
A strong European contingent is headed by Spain's Sergio Garcia, with Darren Clarke and Nick Faldo paired together.
Other British stars trying their luck at Bay Hill are Brian Davis, David Howell, Graeme McDowell, Ian Poulter, Phil Price, Justin Rose and Greg Owen.