Spieth's game first went to shit when he started chasing distance. he got caught up in it like a lot of dudes. he started spraying it all over the place, and his short game couldn't always bail him out. this really fucked with his head. this is when you started seeing all those discussions where Greller was shaking his head because Spieth wanted to play hero ball instead of playing smart.
then came the injuries. then came the children. he just hasn't been right with ball in a while.
in his first five Masters (2014-18), he went T2, 1, T2, 11, 3. i think most had him slotted for at least 4 green jackets when all was said and done.
since then, like his game, it's been Jekyll and Hyde: T21, T46, T3, CUT, T4, CUT, T14.
if there's ever a major he can win, it's Augusta. mainly because there's no rough and he knows the place like the back of his hand. but dude needs to win some regular tour stops, like the Valero Texas Open or the Byron Nelson or Colonial. something to get his head right.