I'll take a look at it.
(Later)
I took all players who played at least 1,000 career games and were not active in 2017, and eliminated seasons with less than 400 plate appearances. Then I compared the season to the career numbers by the sum total of the absolute difference between the season and the career batting average, the season and the career on base percentage, and the season and career slugging percentage.
The LARGEST differences ever were by two 19th century players, Hugh Duffy in 1894 (478 points) and Tip O'Neill in 1887 (440 points), followed by (3) Barry Bonds, 2004, 434 points, (4) Barry Bonds, 2002, 401 points, (5) Willie Keeler, 1907, 389 points, (6) Chuck Klein, 1940, 387 points, (7) Ed Delahanty, 1892, 385 points, (8) Barry Bonds, 1986, 380 points, (9) Norm Cash, 1961, 375 points, (10) Adam Dunn, 2011, 363 points, and (11) Barry Bonds, 2001, 357 points.
That is the opposite of what you had asked about, of course, but this is just my habit. . .to put out all of the incidental stuff I found while looking for X first, and then work toward the actual question. The SMALLEST difference ever is for Johnny Callison, 1969, 2 points, and at this point I remember that I have done this stufy before because I remember finding that before. The second-smallest difference ever was by Jack Doyle, 1899, 3 points, and the third-smallest ever was by Earl Battey, 1964, also 3 points. That seemed kind of interesting because Battey and Callison were both on the bench as young players for the 1959 White Sox, and both got traded away that winter--as did Norm Cash; Cash, Callison, Battey and a couple of other good young players all got sent packing by the White Sox that winter. John Romano. . .I don't remember who all.
Anyway, in 4th place is Steve Sax, 1982, who is in fact a rookie, so his rookie numbers predict his career numbers even better than Reese's--3 points total discrepancy, as opposed to 8. Sax hit .282 as a rookie with a .335 on base percentage, .359 slugging, whereas in his career he hit .283, .335,.358. It is three points total if you save more decimals.
Three other rookies also came closer than Reese--Gus Bell in 1950 (5 points), Luis Aparicio in 1956 (6 points) and Tommy Harper in 1963 (8 points). Don't actually know whether Harper is ahead of Reese or behind him if you save more decimals.