Sport can be funny like that; a nobody one day, talk of the town the next. In the days, and years, to come Agar, chosen for his left arm spin ability and playing just his 11th first-class game, may reflect back on the one that got away.
Then again, maybe not. Agar has some form, admittedly at a lower level, with the bat. His innings yesterday may turn out to be rather more than a one-off.
Consider that last summer Agar banged 108 for the University of Western Australia, having arrived at 58 for five. Also take note of an unbeaten 34 off 101 balls on first-class debut against New South Wales in January, at No 10.
And add in 71 not out against Tasmania soon after, which took WA from 203 for six to 358 for eight and an improbable two-wicket win.
Handing him his first cap was a bold stroke from coach Darren Lehmann and captain Michael Clarke, which produced a hugely unexpected dividend. In 10 previous first-class games, Agar took 31 wickets at 29.3, what might be termed a steady start, no more.
This is shaping up as a difficult tour for Australia. They're not rated to foot it with confident (too confident?) England over five tests. But the selection of Agar has given the tourists a fillip, both in terms of discovering a young talent and perking up the mood in the camp. This latter element shouldn't be written off lightly.
Next thing you know Australia will be calling for a rapid promotion up the batting order. One thought on that: another left arm spinner's first test innings, in 1997 against England, was at No 11. Six hundreds and 4500 runs later, that's a speck in the rear view mirror for Dan Vettori.