ROY

This is a bumper year for rookies in the National League, right? Third baseman Maikel Franko's been a bright spot for a bad Phillies club. Mets pitcher Noah Syndergaard has Citi Field fans wearing Thor outfits to his starts. Randal Grichuk has emerged a stalwart for the Cardinals, putting up the team's best hitting numbers while playing all three outfield positions. And, of course, the two shining stars have been Cubs third baseman Kris Bryant and Dodgers center fielder Joc Pederson--both All-Stars, both Home Run Derby competitors. The National League Rookie of the Year award is a two-horse race between that duo.

That is SO June.

Here are Bryant and Pederson through June 30:

Player	AB	R	H	2B	3B	HR	RBI	BB	SO	SB	CS	BA	OBP	SLG	OPS	WPA
Kris Bryant	247	41	68	13	2	10	43	40	87	6	2	.275	.381	.466	.847	+2.7
Joc Pederson	262	45	64	12	1	20	38	55	94	2	5	.244	.384	.527	.911	+1.2

Provided by Baseball-Reference.com: View Play Index Tool Used
Generated 8/8/2015.

(WPA, as I explained in this article, is a measure of clutch hitting, reflecting the cumultative increase in expected winning percentage the player added on offense.)

And here they are since:

Player	AB	R	H	2B	3B	HR	RBI	BB	SO	SB	CS	BA	OBP	SLG	OPS	WPA
Kris Bryant	113	15	21	4	2	4	18	17	44	5	1	.186	.304	.363	.667	+0.6
Joc Pederson	103	8	27	6	0	1	5	11	36	0	1	.165	.265	.252	.517	-0.7

Provided by Baseball-Reference.com: View Play Index Tool Used
Generated 8/8/2015.

Bryant has fallen off the table, while Pederson's been one of the worst hitters in the league. His .517 OPS since the end of June is worse than the full-year OPS of his teammate Zack Greinke (.531) who is, of course, a pitcher. The two young stars' declines has created a more wide-open National League Rookie of the Year race.

Here is a list of the leading National League rookie hitters with a minimum of 250 plate appearances, ranked by OPS+, which is on base percentage plus slugging percentage, adjusted for home park, scaled to 100 (i.e., 100 = league average):

Rk	Player	OPS+	Tm	AB	R	H	2B	3B	HR	RBI	BB	SO	SB	CS	BA	OBP	SLG	OPS	Pos
1	Randal Grichuk	146	STL	261	40	75	20	7	14	43	16	87	4	1	.287	.335	.579	.913	LF
2	Matt Duffy	129	SFG	352	48	109	20	4	9	51	16	63	5	0	.310	.348	.466	.814	3B
3	Maikel Franco	128	PHI	284	42	80	21	1	12	47	24	48	1	0	.282	.343	.489	.832	3B
4	Jung Ho Kang	126	PIT	293	40	86	17	2	8	35	21	66	5	3	.294	.366	.447	.813	3B/SS
5	Joc Pederson	122	LAD	365	53	81	18	1	21	43	66	130	2	6	.222	.352	.449	.802	CF
6	Kris Bryant	119	CHC	360	56	89	17	4	14	61	57	131	11	3	.247	.357	.433	.790	3B
7	Yasmany Tomas	106	ARI	312	32	93	17	2	6	39	14	81	5	2	.298	.331	.423	.754	RF/3B
8	Odubel Herrera	104	PHI	318	41	91	22	3	5	29	12	77	9	4	.286	.317	.421	.739	CF
9	Jorge Soler	98	CHC	297	30	80	18	1	5	34	24	99	3	1	.269	.326	.387	.713	RF
10	J.T. Realmuto	82	MIA	297	32	73	15	5	6	29	12	48	4	3	.246	.276	.391	.666	C

Provided by Baseball-Reference.com: View Play Index Tool Used
Generated 8/8/2015.

Not so much a Bryant/Pederson duopoly anymore, is it? Of particular note to Pirates fans, consider Jung Ho Kang. The signing of the Korean Baseball Organization star was a head-scratcher, given that :

1. No batter has ever gone from the KBO to the majors. (There have been Korean-born major leaguers, but every hitter was drafted by an MLB team.)
2. His Playstation-like numbers from last year with the Nexen Heroes (.356/.459/.739 slash line, 40 homers and 117 runs batted in during 117 games played) were the product (by the league's admission) of a juiced ball. 
3. He was a shortstop in Korea, but the Pirates already had Jordy Mercer well-established there.
4. He has the arm to play third, but the Pirates had last year's breakout star, Josh Harrison, ensconced there. 

All told, his four-year, $10.75 million contract (with a $5.5 million team option for a fifth year), on top of the $5 million posting fee the Pirates paid to Nexen for the right to negotiate with Kang, seemed out of place for the low-budget Pirates. Where would he play? How likely was it that he could hit?

At this point, I think we can safely say three things about Kang:

1. He has absolutely been a lifesaver for the Pirates. He played a fair amount of shortstop early in the season, as Mercer struggled to get his batting average above .200. (He didn't get there until June.) Then he took over third when Harrison had thumb surgery on July 6. And when Mercer sprained his knee on July 19, Kang became the everyday shortstop.
2. He's been one of the Pirates' best players. Baseball-Reference, FanGraphs, and Baseball Prospectus all rate him as the Pirates' second best position player (after Andrew McCutchen) in overall value.
3. As the table above indicates, he's a Rookie of the Year candidate. He's third in batting, first in on base percentage, and fifth in slugging among rookie hitters, all while playing a more important defensive position, and playing it well, than most.

If the season ended today, I'd expect Bryant to win Rookie of the Year. But the season isn't ending today. There's still time for the surprising Kang (check out the graphs in this article) to make up more ground.