Thinking these five may have some of the closest batting average differences between the two halves of career?
Joe Root (+0.09)
1st half: 76 tests, 6455 runs @ 50.82
2nd half: 76 tests, 6517 runs @ 50.91
Doug Walters (+0.91)
1st half: 37 tests, 2774 runs @ 47.82
2nd half: 37 tests, 2583 runs @ 48.73
Mark Waugh (-1.66)
1st half: 64 tests, 4261 runs @ 42.61
2nd half: 64 tests, 3768 runs @ 40.95
Allan Border (-1.72)
1st half: 78 tests, 5909 runs @ 51.38
2nd half: 78 tests, 5265 runs @ 49.66
Geoff Boycott (-1.75)
1st half: 54 tests, 3940 @ 48.64
2nd half: 54 tests, 4174 @ 46.89