"But he seems to have been someone who's come on in leaps and bounds for New Zealand cricket, and leading their attack with aggression, which is great to see," he added.
Elgar scored a century at Port Elizabeth in 2013, Wagner's first test against his former countrymen, but the Wagner of four years ago was a very different animal from the bowler who has scrapped his way up to No 11 in the test bowling rankings.
His story is a testament to a determined, resilient character utterly determined to make the very best of his new life.
Wagner's overall test record is impressive, but dig a little deeper and it's outstanding.
In his past 14 tests - that is, from the time he had a seven-month break in the second half of 2014 - Wagner has taken 63 wickets at an outstanding 23.09 average.
His ability to unsettle the best batsmen with hostility at a sharp, if not blistering pace, along with an uncanny ability to deliver short-pitched bowling which doesn't break the bouncer rule, has made him indispensable for New Zealand.
And when he said this test was just another test, don't believe a word of it. It's his home ground, against his former homeland. It matters.
"Any time you are putting a black cap on your head it is a special occasion; the cherry on top is it's at my home ground."
Wagner has had to fight the clock to make the start tomorrow, after fracturing a finger in a Ford Trophy match at the start of February. Yesterday the ring finger was in a protective wrapper.
He won't be wearing it in the test.
"It's just a precaution when I'm batting or knocking it against something. You don't want to get unnecessary blows on it."
South Africa's bowling attack will be spearheaded by young star Kagiso Rabada and seasoned quality seamer Vernon Philander, with either the tall Morne Morkel, back from injury, or Duanne Olivier, who took five Sri Lankan wickets in his only test in January, completing the fast-medium trio.
Philander has taken 32 wickets at just 15 apiece in six tests against New Zealand. Green, seamy conditions will suit him to a tee.
Another New Zealander who likes University Oval is senior batsman Ross Taylor, who averages 78 in his six tests there.
New Zealand are unbeaten at University Oval going into their eighth test. They have something to protect, but as Elgar mischievously put it yesterday "that's something for us to try and correct".
Strong standing
•Neil Wagner has taken 118 wickets in 29 tests at 28.58
•Born in South Africa, Wagner has played three tests against his former homeland, taking 10 wickets.
•He's ranked 11th in the world among test bowlers, the highest ranking of New Zealanders. Fellow seamers Trent Boult and Tim Southee are ranked 12th and 13th.
