The Floridian's strongest performance in round three, a six-under round of 65, had powered him to a one-shot lead for the final day.
Lahiri, who had holed a whole lot of long and crucial putts on Saturday, bore the brunt of the firm Sunday greens at the Riviera, and it cost him dearly. On the back nine, he made three birdies, including a key one on the 16th, where he made a 30-foot putt.
Looking for a strong finish, Lahiri began well with birdies on first and third holes at which point a Top-10 finish looked realistic. Then he saved par with 7-foot putts on the 12th hole (the most hard hole of the week) and the 13th (the fifth most-difficult) before his dramatic hole-out at 14. And he was 1 over on his round at the turn, sitting two shots back of Cantlay at the time.
There, on the 18th green at Riviera Country Club, after winning the Genesis Open, these tears were a sign of something much bigger.
But he steadied his leaky ship with a 10-foot birdie at the par-five 11th, and then took a two-shot lead when his 50-foot bunker shot at the 14th clattered against the pin and dropped in.
Watson also won the Genesis Open in 2014 and 2016.
It was also the first wins for both men in two years.
Watson showed up this year at No. 117, coming off a year filled with so many doubts that he says he discussed retirement with his wife many times.
He is certainly one to watch out for at this year's U.S. Masters given his recent form and has fond memories of Augusta, winning the Silver Cup in 2012.
Watson stayed in the game with three key putts early on the back nine, then fulfilled a playful pledge he forgot he even made on the par-3 14th by holing a bunker shot for birdie that allowed him to seize control Sunday in the Genesis Open. The UCLA alum could do no better than pars the rest of the way for a 71 to tie for fourth with Scott Stallings (68).
Woods did well to save par at 18 before finding the green in two at the long first and two-putting from almost 50 feet for his fourth birdie of the day, but another errant tee shot at the fifth followed by a misjudgement from the middle of the fairway at the seventh both led to bogeys. Mickelson (68) tied for sixth. Mickelson has finished in the top-10 on each of his last three starts. "My goal was always to get to 10 wins and this got me to my 10th win".
More unbelievable was the fact that the ball went in at all given how Watson's bunker play had been pretty awful thus far in 2017-'18. "We don't know if I'm ever going to win again, if I'm going to win 100 times, we just don't know". "He said, 'how do you putt?' I said, 'I don't know.' He said, 'well, aim it to the right when it breaks to the left, aim it to the left when it breaks to the right, ' exactly how you imagine your golf ball in the fairway or off the tee, however you imagine it, imagine it that way".