Are you talking about the playoffs (he hasn't played as well as he can lately), or this year - his 15th? Playoffs are a pretty short sample .. a few games. If it's this year you're talking about, his 3pt shooting is actually better (.357) than his career average ((.347). And his EFGP is pretty close to his average over 15 seasons. These numbers don't exactly show someone's who's falling off the ledge or sucking.
2003-04 19
DEN NBA SF 82 82 2995 624 1465 .426 69 214 .322 555 1251 .444
.449 408 525 .777 183 315 498 227 97 41 247 225 1725
2004-05 20
DEN NBA SF 75 75 2608 530 1230 .431 42 158 .266 488 1072 .455 .
448 456 573 .796 141 285 426 194 68 30 224 229 1558
2005-06 21
DEN NBA SF 80 80 2941 756 1572 .481 37 152 .243 719 1420 .506
.493 573 709 .808 122 272 394 216 88 42 218 229 2122
2006-07 22
DEN NBA SF 65 65 2486 691 1453 .476 40 149 .268 651 1304 .499
.489 459 568 .808 143 248 391 249 77 23 234 203 1881
2007-08 23
DEN NBA SF 77 77 2806 728 1481 .492 58 164 .354 670 1317 .509
.511 464 590 .786 178 393 571 259 98 39 253 253 1978
2008-09 24
DEN NBA SF 66 66 2277 535 1207 .443 63 170 .371 472 1037 .455
.469 371 468 .793 106 344 450 222 75 24 199 195 1504
2009-10 25
DEN NBA SF 69 69 2634 688 1502 .458 59 187 .316 629 1315 .478
.478 508 612 .830 152 302 454 222 88 30 209 225 1943
2010-11 26 TOT
NBA SF 77 77 2751 684 1503 .455 95 251 .378 589 1252 .470
.487 507 605 .838 118 445 563 221 68 46 206 224 1970
2010-11 26
DEN NBA SF 50 50 1774 437 967 .452 42 126 .333 395 841 .470
.474 343 417 .823 77 305 382 140 43 31 142 134 1259
2010-11 26
NYK NBA SF 27 27 977 247 536 .461 53 125 .424 194 411 .472
.510 164 188 .872 41 140 181 81 25 15 64 90 711
2011-12 27
NYK NBA SF 55 55 1876 441 1025 .430 68 203 .335 373 822
.454 .463 295 367 .804 88 256 344 200 62 24 144 156 1245
2012-13 28
NYK NBA PF 67 67 2482 669 1489 .449 157 414 .379 512 1075
.476 .502 425 512 .830 134 326 460 171 52 32 175 205 1920
2013-14 29
NYK NBA PF 77 77 2982 743 1643 .452 167 415 .402 576 1228 .469
.503 459 541 .848 145 477 622 242 95 51 198 224 2112
2014-15 30
NYK NBA SF 40 40 1428 358 806 .444 61 179 .341 297 627 .474 .
482 189 237 .797 72 192 264 122 40 17 89 87 966
2015-16 31
NYK NBA SF 72 72 2530 567 1307 .434 105 310 .339 462 997 .463
.474 334 403 .829 98 458 556 299 62 38 176 180 1573
2016-17 32
NYK NBA SF 74 74 2538 602 1389 .433 151 421 .359 451 968 .466
.488 304 365 .833 62 376 438 213 60 34 153 198 1659
2017-18 33
OKC NBA PF 78 78 2501 472 1168 .404 169 474 .357 303 694 .437 .
476 148 193 .767 67 386 453 103 47 49 99 197 1261
Career NBA 1054 1054 37835 9088 20240 .449 1341 3861 .347 7747 16379 .473
.482 5900 7268 .812 1809 5075 6884 3160 1077 520 2824 3030 25417
8 seasons DEN NBA 564 564 20521 4989 10877 .459 410 1320 .311 4579 9557 .479
.478 3582 4462 .803 1102 2464 3566 1729 634 260 1726 1693 13970
7 seasons NYK NBA 412 412 14813 3627 8195 .443 762 2067 .369 2865 6128 .468 .
489 2170 2613 .830 640 2225 2865 1328 396 211 999 1140 10186