Ashwin last played an ODI more than 18 months ago, and his selection is a chance for the team management to have him ready, along with Washington, should they need to replace Axar Patel, who has a left quadriceps strain
that ruled him out of the Asia Cup final.
Ashwin has been training at the NCA over the past week along with spin consultant Sairaj Bahutule, apart from regular physical conditioning work, even as the national team was away in Sri Lanka.
"We're hoping Axar will be fit," chief selector Ajit Agarkar
said. "Washy was already part of the squad for the final. Ashwin brings experience, so it gives us options in case there is a need at some stage for us to look at those guys."
Rohit elaborated on the Ashwin selection a bit more when asked if the offspinner's lack of match-time in the format could be a possible hindrance.
"With guys like Ashwin, game-time and time on the ground is not so much of a concern," he said. "Which is why we thought if he is an option for us, we need to get him in. With the kind of experience he has, for guys like him, it's all in the head more than the body. I thought getting him in could give is a chance to understand where he is at, how his body is and stuff like that.
"It's not like he has not been playing cricket for the last year or so. Yes, he hasn't played in this [ODI] format, but he played Test cricket recently in the West Indies, and if I'm not wrong, in the TNPL as well. Of course, there's no comparison but he has had some cricket there. The games against Australia will give us a chance to look at where he's at."
Explaining the team management's rationale behind naming two different squads for a short ODI series, Agarkar stressed the importance of giving the senior players a "mental break" given the short turnaround between their victorious Asia Cup campaign and the first ODI.
"Luckily we got a fair amount of cricket at the Asia Cup," Agarkar said. "If not, we would've looked at it some other way. More than physical, sometimes guys need a mental break, which isn't a bad thing leading into a tournament like the World Cup.
"For the third game, everyone will be available. We will play our World Cup squad. This [squad for the first two ODIs] gives us a chance to give guys sitting outside a chance. It's still a strong squad. Like I said, if we hadn't got a lot of cricket at the Asia Cup, who knows, we may have thought differently."
With Rohit resting, India have the option of picking either Ishan Kishan or Ruturaj Gaikwad
as an opener. Gaikwad has been training at the NCA along with the rest of India's Asian Games contingent that will leave for China on September 27. Gaikwad, who is set to captain that team, will now link up with the rest of the touring group immediately after the second ODI in Indore on September 24.
The Australia series, which begins on September 22, is India's last ODI assignment before the World Cup and it presents a chance for highly-rated middle-order batter Tilak Varma
to push his case at the highest level. He has been picked for the first two games.
India's squad for Australia series
For first two ODIs: KL Rahul (capt), Ravindra Jadeja (vice-capt), Shubman Gill, Ruturaj Gaikwad, Shreyas Iyer, Ishan Kishan, Suryakumar Yadav, Shardul Thakur, Jasprit Bumrah, Mohammed Siraj, Mohammed Shami, Tilak Varma, Prasidh Krishna, R Ashwin, Washington Sundar
For third ODI: Rohit Sharma (capt), Hardik Pandya (vice-capt), Shubman Gill, Shreyas Iyer, KL Rahul, Ishan Kishan, Suryakumar Yadav, Ravindra Jadeja, Shardul Thakur, Jasprit Bumrah, Mohammed Siraj, Mohammed Shami, Virat Kohli, Kuldeep Yadav, Axar Patel (subject to fitness), R Ashwin, Washington Sundar
Shashank Kishore is a senior sub-editor at ESPNcricinfo