Not top 20, but I think every Spurs fan has to be thrilled with how much better he's looked this season compared to last. He's taking less shots (9.3 FGA per game) and when he does shoot, he's being extremely efficient. Career low in TOs, and career high in TS%. As for his assists, the raw numbers look a bit low, but per 36 they're about in line with his career averages, which is fine.
But honestly, the biggest surprise has to be his defense. The past couple of years he was a complete liability on that end and I cringed every time he was guarding someone with the ball. This year though he's actually been incredibly solid (at least by Parker standards

) defensively. Obviously it helps when you have Green/Kawhi/Aldridge/Duncan behind you helping out, but regardless, he deserves credit for making strides on that end.
I have doubts about him keeping this up all season, but if he can at least keep up the defensive effort without completely falling apart efficiency-wise (55-57 TS% would be good enough), I'll be ecstatic.