Why are some baseball players inconsistent by the month? Reasons?

Code:
April						
Chris Dickerson	        .205 .321 .341 .662
Brandon Phillips	.188 .293 .319 .612
Joey Votto		.346 .411 .568 .979
Johnny Gomes		Minors	
Wladimir Balentien 	.310 .323 .448 .771 Seattle
Ryan Hanigan		.357 .438 .429 .867
Adam Rosales		.500 .500 .500 1.000 2 AB
Paul Janish		.357 .438 .429 .867
Laynce Nix		.310 .355 .621 .976
Willy Taveras		.262 .351 .338 .689
Jay Bruce		.258 .338 .530 .868
Ramon Hernandez	        .246 .303 .344 .647
Drew Sutton		Minors			

May						June
Chris Dickerson	        .271 .417 .396 .813	Chris Dickerson	        .333 .394 .429 .823
Brandon Phillips	.352 .392 .682 1.074	Brandon Phillips	.253 .325 .394 .719
Joey Votto		.378 .541 .733 1.274	Joey Votto		.321 .387 .500 .887
Johnny Gomes		.375 .444 .438 .882	Johnny Gomes		.327 .424 .636 1.060
Wladimir Balentien 	.209 .260 .328 .588	Wladimir Balentien 	.205 .279 .385 .664
Ryan Hanigan		.314 .410 .392 .802	Ryan Hanigan		.318 .400 .379 .779
Adam Rosales		.241 .327 .356 .683	Adam Rosales		.079 .178 .079 .257
Paul Janish		.269 .345 .346 .691	Paul Janish		.148 .179 .185 .364
Laynce Nix		.242 .304 .484 .788	Laynce Nix		.254 .299 .493 .792
Willy Taveras		.269 .307 .333 .640	Willy Taveras		.167 .167 .208 .375
Jay Bruce		.212 .276 .487 .763	Jay Bruce		.187 .292 .385 .677
Ramon Hernandez	        .312 .383 .419 .802	Ramon Hernandez	        .174 .283 .314 .597
Drew Sutton		Minors			Drew Sutton		Minors

July						August
Chris Dickerson	        .215 .292 .277 .569	Chris Dickerson	        .375 .459 .469 .928
Brandon Phillips	.273 .314 .455 .769	Brandon Phillips	.197 .254 .311 .565
Joey Votto		.324 .352 .598 .950	Joey Votto		.188 .291 .290 .581
Johnny Gomes		.213 .304 .525 .829	Johnny Gomes		.239 .286 .587 .873
Wladimir Balentien 	.095 .208 .238 .446	Wladimir Balentien 	.282 .378 .385 .763
Ryan Hanigan		.297 .395 .324 .719	Ryan Hanigan		.140 .218 .200 .418
Adam Rosales		.273 .304 .545 .849	Adam Rosales		.212 .305 .346 .651
Paul Janish		.176 .333 .176 .509	Paul Janish		.148 .207 .148 .355	
Laynce Nix		.175 .242 .263 .505	Laynce Nix		.333 .367 .578 .945
Willy Taveras		.250 .273 .271 .544	Willy Taveras		.222 .236 .241 .477
Jay Bruce		.138 .138 .241 .379	Jay Bruce		DL	
Ramon Hernandez	        .273 .350 .303 .653	Ramon Hernandez	        DL	
Drew Sutton		.071 .133 .143 .276	Drew Sutton		.214 .267 .357 .624



Season
C. Dickerson	.274 .369 .373 .742
B. Phillips	.260 .320 .445 .765
Joey Votto	.308 .388 .535 .923
Jonny Gomes	.270 .351 .567 .919
W. Balentien	.275 .370 .375 .745
Ryan Hanigan	.275 .364 .335 .699
Adam Rosales	.209 .293 .323 .616
Paul Janish	.207 .285 .243 .528
Laynce Nix	.254 .306 .470 .776
Jay Bruce	.207 .283 .441 .724
R Hernandez	.249 .330 .355 .685
Drew Sutton	.167 .222 .286 .508
Willy Taveras	.238 .273 .284 .557


Janish Minor League
2008 25 Louisville IL AAA 	.252 .324 .387 .711
2007 24 Louisville IL AAA	.221 .278 .317 .594
2007 24 Chattanooga  AA	        .244 .358 .330 .688

Sutton Minor League
2009 26 2 Teams 2 Lgs AAA       .262 .382 .453 .835
2008 25 Corpus Christi AA	.317 .408 .523 .931
2007 24 Corpus Christi AA	.269 .351 .388 .738