A 56-year-old from Spain, Canizares birdied five of his first six holes around a bogey at No. 4. But he played the final 12 in 1-over as he seeks his second Champions Tour victory and first since the 2001 Toshiba Classic.
Canizares failed to crack the top 15 in his first six starts this season, then tied for third at the Toshiba Senior Classic at the end of March. He followed with finishes of 50th and 51st in his next two events but was sixth last week at the Kinko's Classic.
Dave Eichelberger and James Mason opened with 2-under 70s to share second place and are one shot in front of Tom Jenkins, Vicente Fernandez and Andy Bean as only six players broke par on the Tom Watson-designed course.
Also hosting the event in his hometown, Watson signed for a 72 that left him tied for seventh place with six others.
The tournament moved to the National Golf Club of Kansas City from nearby Tiffany Greens Golf Club, where Bruce Lietzke won a rain-shortened, 36-hole event last season.
Lietzke played 14 holes at 9-over Friday before withdrawing due to tendinitis in his right elbow.