Funk, a winner last month on the Champions Tour, leads the PGA TOUR's first- ever event in Mexico by two shots over four players. Not bad considering Funk wasn't sure which tour he would be playing this week.
'It turned out to be a really good decision based on the first round,' Funk said.
In all, there are 22 players within five shots of the lead after the first round.
But they are all looking up at Funk, who won his second Champions Tour title last month at Turtle Bay, then missed the cut at the PGA TOUR's Nissan Open last weekend.
Playing with the seniors would have guaranteed Funk three rounds of good practice, but he made a commitment before the season started to play in Mexico this week.
By shirking the Champions Tour, he became one of the better-known golfers in the field at El Camaleon while the top 64 players in the world are playing in the Accenture Match Play Championship in Arizona.
'They had used me in a lot of print media guides and stuff, and I had to honor my first commitment so I decided come down here,' Funk said.
The decision paid off. Not only is Funk all but guaranteed four rounds of golf, but he opened the tournament by matching the second-best score of his PGA TOUR career.
It began at No. 1 when Funk hit a sand wedge to 15 feet to set up the first of his eight birdies. He made back-to-back birdies twice over the next six holes, with each one coming on putts inside 10 feet.
Funk knocked a 6-iron within 6 feet at the 10th, then rolled in a 20-foot putt at the 12th for another birdie, his seventh.
'That was a great birdie,' he said.
He finished his round with a birdie at the 18th, knocking a 7-iron within 10 feet after stringing together five straight pars. It was a fitting end to a flawless round.
'I actually played some of the difficult holes really well today, which was obviously one reason I went so low,' said Funk, who claimed an international title at the 1993 Mexican Open.
Funk went out in an early threesome with two other PGA TOUR veterans, Mark Calcavecchia and Jeff Sluman. All three started strong -- Sluman was beating Funk after five holes -- but only Funk managed to keep it up.
Calcavecchia, in particular, struggled late in the round. An errant drive at the 17th led to a double-bogey, which was followed by a bogey at the 18th as Calcavecchia dropped into a tie for 56th place at even-par.
'If you don't carry it off the tee [here],' Funk said, 'it's going to cost you probably two shots.'
Sluman is tied for 14th place with nine other players at 3-under 67. Ahead of them, two players whose fathers compete with Funk on the Champions Tour -- Kevin Stadler and Bill Haas -- share ninth place with three others at 4-under 66.