The two-time Australian Open victor has had an indifferent start to this season with four missed cuts from seven starts, including last week at Torrey Pines.
Haas fired an eagle and five birdies to edge ahead of compatriot Rickie Fowler in a chasing pack of five on Thursday.
He'll face some stiff competition this week, including from Jordan Spieth, Jon Rahm and Justin Thomas.
While the Phoenix Open is known as a party thanks to the par-3 16th, Spieth doesn't prepare any differently for this tournament than he does his other events. "Just one of those days where they went in for me, so hopefully it will be one of those weeks". After some stops and starts, the tournament has been held continuously since 1944 and at its current location since 1987.
That good play also got him into the interview room and he revealed: "It was a continuation of last week, I hit the ball really well, putter wasn't quite there last week". "I was playing pretty nervously at the start, but I ended up doing better than I thought".
Fowler, a playoff loser to Matsuyama two years ago, also eagled the 15th, where he warmed to his task on a brisk morning, lashing a five-wood to inside two feet.
"Next thing we saw, everyone just went rushing to the side", witness Seth Norris told the Arizona Republic.
This year's Waste Management Phoenix Open finishes Sunday.
The par 3 16th hole at the Waste Management has taken on a life of its own, with its unique stadium environment that accommodates up to 16,000 spectators. "He's so good at understanding", DeChambeau said.
Four golfers are three-time winners at the Phoenix Open, including Gene Littler, Mark Calcavecchia, and Phil Mickelson, though Palmer is the only one to do it three times in a row, from 1961 to 1963. That's one shot to the green and four while on it, if you're keeping track.
Despite going into the tournament feeling particularly confident in his short game, Matsuyama was up and down on the TPC Scottsdale greens, leading him to card five birdies and three bogies, putting him in a share of 29th place.