Jimmy's had the scores to win for the last couple years - he's been 36th, 57th, 42nd in scoring average the past 3 seasons - he just hasn't despite 15 top tens and that crazy made cut streak he had in '12-'13. Was crazy underrated last year, for example. Never put it together for a full week though. Main thing he's doing this season is hitting his putts; he's at 1.20 strokes gained putting this year after being ~0.30 the previous three seasons. Almost a stroke/round is an enormous difference in terms of scoring - the difference between Tiger and an average Tour pro is like 2.5 strokes the last couple years.
Real question is whether he can keep it up. No one has ever sustained that kind of putting season, or even anywhere close without being a stud putter beforehand. Guessing Walker falls off.