I was wondering if this was an unusual drop-off, so checked the figures for all batsmen who played at least 30 Tests; biggest fall in average from first half of career to second half (for those who played in an odd number of Tests, I counted the middle Test in both halves):
Code:
First half Second half Diff
M Runs ave Runs ave Runs ave
JC Adams 54 : 1963 61.34 : 1049 25.59 : 914 35.76
LG Rowe 30 : 1293 61.57 : 754 29.00 : 539 32.57
G Gambhir 58 : 2760 57.50 : 1394 27.33 : 1366 30.17
AR Morris 46 : 2097 61.68 : 1436 34.19 : 661 27.49
RN Harvey 79 : 3833 60.84 : 2383 36.11 : 1450 24.74
VS Hazare 30 : 1420 59.17 : 772 35.09 : 648 24.08
Mominul Haque 34 : 1456 56.00 : 1077 32.64 : 379 23.36
MS Sinclair 33 : 1060 42.40 : 582 21.56 : 478 20.84
AC Gilchrist 96 : 3073 59.10 : 2497 38.42 : 576 20.68
Q de Kock 40 : 1402 50.07 : 996 30.18 : 406 19.89
PH Parfitt 37 : 1113 50.59 : 807 31.04 : 306 19.55
AH Jones 39 : 1703 54.94 : 1319 35.65 : 384 19.29
MJ Greatbatch 41 : 1291 43.03 : 905 23.82 : 386 19.22
KL Rahul 34 : 1200 44.44 : 705 26.11 : 495 18.33
Sadiq Mohammad 41 : 1630 46.57 : 1052 28.43 : 578 18.14
MJ Horne 35 : 1262 38.24 : 652 20.38 : 610 17.87
AI Kallicharran 66 : 2611 53.29 : 1788 35.76 : 823 17.53
Mohsin Khan 48 : 1540 46.67 : 1169 29.23 : 371 17.44
PE Richardson 34 : 1284 45.86 : 777 28.78 : 507 17.08
IJL Trott 52 : 2126 53.15 : 1709 36.36 : 417 16.79
Interesting to see that two of the top four declines were by Morris and Harvey, who played for the same side in the same era. I wonder if it is possible to investigate the extent to which their reduction in output was due to:
a) A decline in their abilities/new technical weakness/bowlers working them out, and
b) More difficult conditions and a higher standard of bowling in Test cricket in the second half of their career.
Certainly, England's attack of the mid to late 1950s was infinitely better than when Morris and Harvey started their Test careers in the 1940s. At the beginning of their career, England's second best bowler was Doug Wright who averaged almost 40 in Test cricket. By the mid 1950s, England had Tyson, Statham, Trueman, Laker, Wardle, Lock and Appleyard all competing for spots. By this time, their bowling depth was so great that many bowlers who were struggling to make the side would have been star bowlers in the 1940s side, if born 10 years earlier. Perhaps you could compare the overall average of Australia's top 6 batsmen in the first and second half of Morris and Harvey's career (excluding Bradman), in order to determine if their batting lineup as a whole also declined by a similar proportion.
Also, I believe Laurence Rowe made over 300 runs on his debut and a seperate triple century. So his performances may not have varied all that much between the first and second half of his career if we ignore the two exceptional Tests.