But based on what the 19-year-old has shown in the first three days of his career, he may not have had his last impact on the first Test at Trent Bridge.
Agar should have finished the third day with three wickets to his name, if not for umpire Aleem Dar inexplicably missing an obvious edge to slip from England's Stuart Broad.
Regardless, Australia couldn't have been much happier with the way Agar followed his heroics with the bat.
He claimed the prized scalp of England captain Alastair Cook for his first Test wicket and 24 balls later struck again to dismiss Jonny Bairstow.
The West Australian's figures of 2-82 from 35 overs for an economy rate of 2.34 were highly impressive, given he has just 10 first-class matches behind him.
Consistency will come.
Dubbed Agar the 'Orrible by the British press, the teenage sensation took his two wickets for just eight runs to leave England in deep trouble, at five down with a lead of just over 100.
"He was obviously nervous in the first innings and didn't get much of a bowl with how things went, but he got into his business today and got going," said teammate Peter Siddle.
"He showed what a quality bowler he is.
"He found his line, found his length and started to bowl some consistent balls. He did build up a lot of pressure there, created enough opportunities, and no doubt he's going to play a big role tomorrow and throughout the rest of the series."
The left-armer was picked for the damage he could do against England's right-hand dominated batting order and he was up to the challenge.
Cool, calm and collected, Agar bowled with the natural fluency that has him tipped as a future star.
Only that stardom has come instantly.
Brought back into the attack in the 60th over, Agar managed to spin one out of the rough and got it to bounce sharply at key man Alastair Cook.
The skipper got a leading edge, and Michael Clarke took the catch, running and diving to his left from first slip.
Then to break the partnership of Bairstow and Ian Bell (43), he slid one beautifully past Bairstow's outside edge and he nicked it behind to Brad Haddin.