The Largest One Year Increases and Decreases in wRC+ For Seasons With 400+ PAs

From FanGraphs.

"Similar to OPS+, Weighted Runs Created Plus (wRC+) measures how a player’s wRC compares with league average after controlling for park effects.  League average for position players is 100, and every point above 100 is a percentage point above league average. For example, a 125 wRC+ means a player created 25% more runs than a league average hitter would have in the same number of plate appearances. Similarly, every point below 100 is a percentage point below league average, so a 80 wRC+ means a player created 20% fewer runs than league average.

wRC+ is park and league-adjusted, allowing one to to compare players who played in different years, parks, and leagues." 

I called up all seasons with 400+ PAs since 1871

Rank	Name	Season	wRC+	Change
1	Babe Ruth	1926	216	83
2	Terry Pendleton	1991	141	81
3	Al Kaline	1955	156	80
4	George Burns	1918	153	79
5	Fred Dunlap	1884	214	78
6	Mookie Betts	2018	185	78
7	Cito Gaston	1970	144	76
8	Adrian Beltre	2004	161	75
9	Roy Campanella	1955	150	75
10	Jimmy Wynn	1972	148	74
11	Scott Brosius	1998	123	73
12	Carl Yastrzemski	1967	194	72
13	Orator Shaffer	1884	176	71
14	Ryan Zimmerman	2017	137	71
15	Clay Dalrymple	1962	120	70
16	Darin Erstad	2000	140	70
17	Cesar Cedeno	1972	163	69
18	Carl Furillo	1953	147	68
19	Pete Runnels	1958	136	68
20	Rico Petrocelli	1969	163	68
21	Aubrey Huff	2010	144	67
22	Willie Stargell	1971	186	67
23	Alex Rios	2012	126	66
24	Cleon Jones	1968	140	66
25	Don Hoak	1957	127	66
26	Kevin Mitchell	1989	185	66
27	Mark McGwire	1992	171	66
28	Sammy Sosa	1998	159	66
29	Stan Musial	1948	201	66

Ruth had his famous stomach ache in 1925, so he performed poorly (by his standards) that year. He returned to form in 1926 (his decline in 1925 from 1924 will be in the next table).

Pendleton in 1991 and Yaz in 1967 are from teams that surprised most people to come in first place. 

The Red Sox went from 72-90 (9th place) in 1966 to 92-70 and 1st place in 1967.

The Braves went from 65-97 (6th or last in the NL West) in 1990 to 94-68 and 1st place in 1991.

I did this analysis initially because I wondered where Lou Gehrig 1927 ranked. He jumped 58 in 1927 to 209. That is tied for the 61st biggest gain along with several other players. That still puts him in the top half of a percent.

Now the largest decreases.

Rank	Name	Season	wRC+	Change
13210	Fred Dunlap	1885	118	-96
13209	Victor Martinez	2015	77	-91
13208	Bryce Harper	2016	111	-86
13207	Mike Epstein	1973	82	-82
13206	Scott Brosius	1997	50	-81
13205	Rogers Hornsby	1926	128	-80
13204	Roy Campanella	1954	75	-79
13203	Babe Ruth	1925	133	-77
13201	Adam Dunn	2011	60	-76
13202	Dick Green	1970	45	-76
13199	Max Carey	1926	57	-75
13200	Sandy Alomar Jr.	1998	56	-75
13198	Chris Davis	2014	94	-74
13197	Jeff Burroughs	1979	87	-73
13195	John Mayberry	1976	94	-72
13196	Ross Youngs	1925	91	-72
13193	Adrian Beltre	2005	90	-71
13194	Reggie Jackson	1983	74	-71
13192	Don Buford	1972	82	-69
13188	Jimmy Wolf	1891	88	-68
13189	Juan Gonzalez	1994	96	-68
13190	Ken Singleton	1984	61	-68
13191	Sixto Lezcano	1980	97	-68
13186	Dick Allen	1975	96	-67
13187	Mark Teixeira	2016	76	-67
13181	Allen Craig	2014	68	-66
13182	Brook Jacoby	1988	78	-66
13183	Hoot Evers	1951	73	-66
13184	Jeff Keppinger	2013	62	-66
13185	Willie McGee	1986	85	-66

Ruth had the 8th largest decrease in 1925. Others who are in both tables in consecutive years are Beltre, Brosius, Campanella and Dunlap.