Smith closed with a bogey on the par-4 ninth.
"A tough hole, especially with the wind blowing," Smith said. "I tried to be aggressive with the driver and hit a natural kind of cut for me down there, but I didn't pull it off and hit it in the fairway bunker and just had to pitch it out. That's really the only option I had."
Making his fifth start on the tour, McKenzie entered the week 64th in the Charles Schwab Cup standings. The top 72 will advance to the playoff opener next week in Richmond, Virginia.
The Australian qualified for the event Monday, shooting a 3-under 69 and winning a three-man playoff for the fourth and final spot.
"Ultimately golf takes care of itself," McKenzie said. "If you play good golf, you don't worry about all those other things. I can't control what everyone else does. All I can do is try and play as well as I can."
Kelly has two victories in his past four starts, taking the Boeing Classic in Washington state and the Pacific Links Bear Mountain Championship in British Columbia for his first senior titles. He also has a tie for sixth and a second-place finish in the four-event run.
"The thing about this tour, is just not stepping on your foot on the first day," Kelly said. "You get off to a good start. If you don't, you can still shoot a 10 under and come back, but the odds are not quite as good. So, you get a decent start, you're within shouting distance and a really good round can put you up."
Charles Schwab Cup points leader Bernhard Langer birdied the last two holes for a 72. The 60-year-old German star is coming off his fifth victory of the season three weeks ago at Pebble Beach. He won in 2012 at Prestonwood.