How does Kedar Jadhav manage to pick wickets?
Kedar Jadhav is a street-smart cricketer. He's played years of domestic cricket and tennis-ball cricket as well. So he knows his game quite well. Technique-wise, owing to his short height and the slingy Malinga-like roundarm action, the ball doesn't bounce as much. Also, since he is a part-time bowler, batsmen tend to take liberties and score easy runs off him. No batsman would be happy if Jadhav concedes four or five runs per over in his quota. So these batsmen try to manufacture certain shots against him; for example, most batsmen try to sweep him and get dismissed because his deliveries don't bounce as much and stay low. This makes playing the sweep a risky proposition.
Also, he bowls wicket-to-wicket, so you either have to play him in the 'V' or have to take the risk of playing across the line. Most batsmen tend to do the latter. It is very important for a bowler to read the batsman. He must be able to anticipate the batsman's next step. I think Jadhav is very good at this. He trapped Steve Smith leg-before-wicket in the fifth ODI and if you would have noticed, he'd read Smith's mind. He anticipates as to when the batsman is going to sweep and changes his length accordingly.
When you have five bowlers in the XI, having the sixth bowler is really a luxury. Every batsman doesn't perform on any given day and it's the same case with the bowlers. This way, Jadhav complements the frontline bowlers by picking up wickets and easing the pressure off them.
Even if he bowls 4-5 overs in the innings, the bowler who's having an off day can be rested. Otherwise, it happens that when you don't have a reliable sixth bowler, the other bowler who has been leaking runs is forced complete his quota of ten overs and that becomes catastrophic, at times, for the team.
And it's not just the cheap overs that he gives, it is also the wickets he picks up. On most occasions, there's no pressure on him. He's a part-timer, keeps wickets as well, and he is in the side, presumably, more for his batting than his bowling. And when he picks up wickets, the confidence that he gains helps when he comes out to bat.
I have also observed that most batsmen tend to sweep him away, which is not a good option against him, in my opinion. Since he bowls wicket-to-wicket and doesn't extract much turn from the surface, it is advisable to hit him as straight as possible. However, batsmen opt for the other route and that, on most occasions, leads to their peril.