American Johnson will become the first player to win all four World Golf Championships events should he defeat young Spaniard Jon Rahm later on Sunday at Austin Country Club.
But Tanihara was unable to sink his birdie putt to prolong the match, enabling Johnson to recover by salvaging par and setting up an eagerly-anticipated showdown with Rahm.
The pair won two holes each on the front nine and then traded pars and a birdie at 12 before Rahm pitched to six feet at the 13th and holed the chance to take the lead for the second time in the match.
United States 42nd seed Bill Haas held off a late charge by countryman Phil Mickelson to defeat the five-time major victor 2 and 1 and reach a Sunday semi-final against 22-year-old Spaniard Jon Rahm, the 21st seed who routed Denmark's Soren Kjeldsen 7 and 5. "These are the biggest events besides the majors, with the best golfers in the world". I really like going to Augusta. "Anything can happen. I like the way I'm playing". "What I saw this week, I just watched the same guy I've watched for five years now", he said.
"I was tested a lot out there but then I didn't give him any holes except for the 10th where I three-putted", he said.
The 22-year-old, who was the world's top-ranked amateur while studying at Arizona State University, is now 25th in the world after winning his first PGA Tour title in the Farmers Insurance Open at Torrey Pines in January.
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Johnson, now a dominant No. 1, was thrilled to survive on another two-match day that left him exhausted.
"I mean, some days it does [feel easy]", Johnson said.
"Even though the match was to decide third place you still want to come out on top, so I was fortunate as I had a few good breaks over the back nine", said Haas. He rolled through his first six matches - losing just eight holes and trailing for just three - before running into Johnson. Johnson won the WGC-HSBC Champions in 2013.
NOTEWORTHY: For the second straight year, all four quarterfinal matches ended before the 18th hole. In the Lone Star State, his firepower was so assertive he didn't trail in any match (he played 112 holes), won the first hole six of seven times, and reached the 18th hole just twice all week.
"Definitely kind of cool to be the first one to win all four".
When he missed the birdie putt, Rahm found himself just two down with thee to play and there was a sense the momentum was in his favour.