Described as "supremely athletic, fast, fearless and with an uncanny sense of anticipation",[1] Kirkpatrick is widely regarded as one of the greatest flankers to have ever played the game.

His try-scoring ability was astonishing; at the time Kirkpatrick played rugby, it was rare for forwards to score tries, but his 16 test tries were an All Black record until Stu Wilson surpassed it in 1983.

[5] He thus became the first All Black to be used as a substitute according to the new International Rugby Football Board regulations[6][7] With his only warm-up being the run down the stairs from the reserve seats, Kirkpatrick scored a hat-trick of tries in a 27–11 victory.

Kirkpatrick has said he was “never comfortable” with apartheid but adopted the position of many leading players at the time and that playing South Africa was the “ultimate challenge”.

[5] In 1971, he was a part of the President's Overseas XV that was chosen to play against England to celebrate the centenary of the Rugby Football Union, scoring two tries in the 28–11 win at Twickenham.

He is to date also the only man to have captained both islands: the South in 1969 in his last season with Canterbury and then the North (in 1972–73) when he had returned home to Poverty Bay.

[13][4][8][14] In 2020 and 2022 he expressed additional concerns about the direction of rugby, including the gladiatorial nature of the game, the massive emphasis on defence, less open play, and the need to be physically big and strong.