Akron - Masters and U.S. Open champion Jordan Spieth, the world number two, will command the spotlight at this week's WGC-Bridgestone Invitational where Rory McIlroy and Tiger Woods are both conspicuous absentees.
Top-ranked McIlroy won last year's tournament at Firestone Country Club by two shots but is unable to defend his title after rupturing a ligament in his left ankle while playing soccer with friends early last month.
Former world number one Woods has triumphed a record eight times at Firestone but is not eligible to compete in the elite (WGC) World Golf Championships event with his ranking having plummeted to a mind-boggling 262nd.
"It's tough. Unfortunately, right now, he's going through a spell where he's not playing that great," Australian world number four Jason Day told reporters about Woods' absence ahead of Thursday's opening round.
"It's kind of weird to not see him playing the events that we're usually used to seeing him playing. This is one of those events that he plays well and wins a lot here.
"Eight times, it's just amazing to even think about. Some guys are just hoping for one WGC win, let alone eight times at one venue."
Spieth would replace McIlroy at the top of the rankings should he triumph at Firestone this week as he also tunes up his game for the year's final major, the PGA Championship at Whistling Straits next week.
"I think it's really good major prep, but at the same time, this is a World Golf Championship," Spieth, 22, told reporters after practising at Firestone on Wednesday.
"This is a huge event. This is one that everyone wants to have on their resume, and there are certainly other goals that come out of trying to win this week too for me personally," said Spieth, who has not yet won a WGC title.
"So ultimately, we're working really hard for this one to try and grab the number one slot."
Forty-eight of the top 50 players in the rankings are competing at Firestone this week, where McIlroy and world number 22 Chris Kirk (broken hand) are the absentees, and they face a challenging layout where the rough is up after recent rain.
"Brutal course, really long, but it looks like we're going to have some good weather this week," said Ohio-based Day, who 10 days ago won his fourth PGA Tour title at the Canadian Open.
"The greens and the fairways should dry out. The greens ... they should be bouncing."