Jordan Spieth flashes No. 1 form as Rory McIlroy looks on

Even the reigning NFL MVP is captivated by the clash of the top two golfers in the world going toe-to-toe at the PGA Championship.

A night after his Green Bay Packers won their preseason opener over the New England Patriots, quarterback Aaron Rodgers was spotted just off the tee box as Jordan Spieth and Rory McIlroy ripped their final tee shots at Whistling Straights in Kohler, Wisc. on Friday.

"It was cool to see him out there," said McIlroy, who noticed Rodgers taking in the final few holes.

McIlroy had an even closer look over the past two days at the man who is zeroing in on stealing the coveted No. 1 spot in the world golf rankings.

Paired together for the second straight day Friday, McIlroy witnessed another nearly flawless round from Spieth, who carded six birdies against one bogey for a 5-under round of 67. Meanwhile, McIlroy overcame a double bogey on the 18th hole, the group's ninth of the day, with an eagle two holes later and finished with a second straight 1-under 71.

Solid, but not good enough to maintain his perch atop the world rankings if the trend continues over the next two days.

"I feel like I played better than the score reflected," said McIlroy. "A little bit annoyed. I feel like there's a lot of ways to get around this golf course.

"Jordan showed that over the past couple of days. He's the prime example of someone whose game is very efficient."

Spieth finished his second round one shot off the morning lead at 6-under, while McIlroy was just outside the top 20 at 2-under.

Should Spieth go on to win the PGA Championship on Sunday, he will leapfrog the Northern Irishman for the top spot in the world. Spieth can also earn the No. 1 ranking for the first time in his career if he finishes in solo second place and McIlroy finishes outside the top 6.

More complex scenarios include Spieth in a two-way tie for second place and McIlroy outside the top 13, and Spieth in a three-way tie for second with McIlroy not among the top 33. With McIlroy safely inside the cut line, Spieth must finish at least in a tie for second to claim the No. 1 ranking.

"Rory is ranked No. 1 in the world, so he's No. 1," said Spieth, who added the two 'get along great.'

"I wouldn't look much into it these first two days other than we're trying to put ourselves in position to win the golf tournament. We don't think much more of it than that."

While McIlroy is coming off a five-week hiatus while recovering from a left ankle injury, Spieth is squarely in the world spotlight at a major championship for the fourth time this year.

"I feel good. I have a chance to win a major championship," he said in response to a question about potential fatigue factoring in over the weekend. "Just thinking about that gives you enough adrenaline that there won't be any issues.

--Japan's Hiroshi Iwata became the 27th player in major championship history to card a round of 63. The 35-year-old recorded an eagle and eight birdies against a lone bogey in his 9-under round. Of the 26 players who have previously shot a round of 63 in a major championship, five have gone on to win.