And after opening rounds of 65 and 66 gave Sharma a two-shot lead at the halfway stage, he added a third round of 69 to finish 13 under par, two ahead of Masters champion Sergio Garcia, five-time major victor Phil Mickelson, Tyrrell Hatton and Rafa Cabrera Bello.
After grabbing control of the WGC-Mexico Championship 2018 on Friday, Shubhankar Sharma kept rolling on Saturday to hold on to the lead heading into the final round.
Mickelson said after the round that his key to success is to miss it in the right place.
Sharma, who opened with a 65, stood on 11-under-par 131, with Spain's Sergio Garcia and Rafa Cabrera Bello and American Xander Schauffele sharing second on 133.
Coetzee is looking for a fourth European Tour title and a second at the Tshwane Open after winning this event in 2015.
Now ranked 75th in the world, he has only four weeks left to move into the top 50 and punch his ticket to Augusta. He added, "I made a few mistakes on the greens but the greens are tough this week so I think everyone's making a few mistakes". Spieth birdied three of his last four holes and was six behind.
Sharma blasted his opening tee shot two feet from the cup for a tap-in eagle.
"Obviously a dream come true for me to be playing in this tournament and obviously leading, that's just fantastic", Sharma said.
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Sharma closed with birdies from three feet ay 16, and 10 feet at the par-3 17th and par-4 18th.
"Then he just realised and said, "So sorry, I thought you were media", and he said "hi", I said hi".
In Mexico players have to adjust for the higher altitude which makes ball travel nearly 15 percent more and then there is distance to be adjusted for uphill layout.
We've come to expect the world's best golfers to hit the ball even farther than usual thanks to the high altitude at this week's WGC-Mexico Championship.
A year after losing a chance to win the event in his PGA Tour Champions debut when his 3-wood went left into the water on the final hole, Stricker did it again Saturday.
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Shubhankar could potentially have a career-changing win with the winner's cheque worth Dollars 1.7 million, an exemption onto the PGA Tour through the 2020-21 season, 550 FedExCup points and starts in nearly every major championship including THE PLAYERS Championship this season.
"I felt like I didn't have a whole lot of control today, but I putted really well", he said.