Ashton Agar's selection for the final Border-Gavaskar Test has not just left certain members of the Australian pace bowling attack looking over their shoulders at the possibility of a second spinner for the SCG.
Even if Agar does not play on January 6, Joe Burns and Shane Watson each have reason to ponder Agar's return to a national team squad for the first time since the 2013 Ashes tour. So too does Glenn Maxwell.
When Agar first toured as an intern in the early weeks of the 2013 India tour, and was then named for his debut against England at Trent Bridge later that year, it was as a left-arm spinner. His enchanting 98 in that match from No. 11 came with all the glorious revelations of a new love, but proved just as fleeting as that can sometimes be.
In the 18 months since, including a somewhat less memorable second Test match at Lord's, Agar has worked assiduously at restyling himself as an allrounder. The road has not always been straight and steady, and the empirical evidence of his development is only subtle. Nevertheless, he returns to the national set-up at a time when the selectors are looking more urgently around for youth and a broad set of skills to balance their teams.
"I like to think of myself as an allrounder yes, more a bowling allrounder but some days you bat better than you bowl ... it's not a bad problem to have," Agar said, following his selection. "I felt like I batted well in the one-day tournament for WA and my last few Shield innings have been reasonably good, and I've been doing a lot of work with Justin Langer with my batting, on my stance and everything really, trying to become a better batter, so if I'm picked to bat as well I'd be comfortable with that."
Langer has watched Agar's growth with interest and plenty of helpful advice. He has been the knowing observer of a comedown that followed Agar's Ashes exploits, a wrestle to regain the former fluidity of his bowling action, and a yearning to improve as a batsman not yet fulfilled by any scores to match that knock in Nottingham.
"You could write a novel about that innings, it was one of the best things I've seen on TV since Gladiator I reckon, it was fantastic," Langer quipped. "But it's all part of the journey as a young player ... he'll be much stronger for the experience of last time. It's very tough when you're dropped for the first time, you can't see past the end of your nose and sometimes it takes a while but he's fought back, he went through the mourning period and now he's back playing really good cricket.
"I don't think he handled it very well, but that's not an Ashton Agar thing, that's like most young players. You're there and all of a sudden it's taken away from you. But you go back in time, our best players have all been through it, Michael Clarke, Ricky Ponting, Damien Martyn, Matthew Hayden, so many good players get it, they have their dream then it gets taken away. So everyone deals with it differently, he probably didn't deal with it as well as he'd have liked, but that's all part of his journey to becoming a mentally tough, strong Australian cricketer."
Agar's return has come about at least partly through the lapses of others. Steve O'Keefe cannot be blamed for falling prey to injury at the wrong moment - not for the first time - but Maxwell's misadventures in the UAE and since then have left Rod Marsh's panel to wonder whether their two-year dalliance with the excitable Victorian have had the desired effect on his game.
They have the experience of Steven Smith to tell them that it is very possible for a talented young player to come back to international cricket after an early taste with a better plan for coping with it and an increased appetite for the hard work required. They may be about to test whether Agar's time away has done this, while also reasoning that it is time for Maxwell to spend some months on the outside, looking in.
Another question for the asking is the balance of Australia's World Cup squad. Nathan Lyon gave a decent audition in the UAE against Pakistan, and Xavier Doherty is the eminently serviceable incumbent. But the elevation of Agar into the limited-overs side for the triangular series that serves as a prelude to the main event is also a possibility currently under consideration.
Whatever the format, it is Langer's belief that Agar should be given a commission where he is expected to offer runs as well as wickets, as required of him for his state where he has commonly batted at No. 7 in recent times. Such a move at the SCG would leave Watson and Burns as two of the men most likely to make way for the sort of experiment occasionally tried in dead Tests - Mitchell Johnson batted seven against Sri Lanka here in the first week of 2013.
"It'd be almost unlike the Australian way to go with two spinners in a Test match. They might play him as an allrounder like we have. So if they go that way it might be a bit different," Langer said. "We bat him in one-day cricket, T20 and Shield cricket at No. 7, so we're trying to give him every opportunity to develop into a really good allround player.
"He's a brilliant fieldsman and as natural a talent I've seen with the bat since Adam Gilchrist, so when he learns how to make runs and stats thinking like a batsman rather than a tail-ender he'll be a fantastic talent there."
The Gilchrist comparison is not made lightly, and it is the kind that enthuses the selectors. It is also something Agar is better prepared to wear this time around, for no longer is he the shooting star of Trent Bridge. "I've got no doubt I was ready for it when I was picked and I'm definitely better for it coming into Sydney if I play," Agar said. "I've had the first Test, that's done and dusted, so I'd be confident coming into it."