Jordan Spieth's putting
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I would say he has a very conventional putting stroke. His putter is in inline with his arms, and his elbows are tucked in towards the side of his body. His posture is pretty relaxed. It does look like he has a left hand low putting grip. That isn't something revolutionary though.
He is an above average putter on tour. Like all good putters he does three things really well.
1) He reads putts well
2) He hits his intended target line
3) He controls his distance on his putts