Speaking to Star Sports, Shastri said India should pick their keeper depending on the composition of their bowling attack. They went with Bharat ahead of Kishan in their most recent Test series, at home against Australia in February-March, and Shastri reckoned they might do the same if conditions at The Oval warrant picking two spinners.
"I have a feeling that India might just go with, depending on who's playing - if two spinners are playing, maybe KS Bharat, but if there are four seamers and one spinner playing, then it'll go the other way, it might go Ishan Kishan's way."
Spin usually comes into play at The Oval, but the catch for India is that the venue usually hosts Test matches during the warmer, drier second half of the English summer. Of the 104 Tests The Oval has hosted since 1880, the vast majority have been played in August and September, with only eight starting in July. The WTC final, which begins on June 7, will be the first-ever Oval Test to be played in June.
Regardless, Shastri indicated he was leaning towards a two-spinner combination, given that the UK has experienced a mostly sunny summer so far. Outside of the wicketkeeper, Shastri was certain about his 12 for the final, with Ashwin and the fast bowler Umesh Yadav battling it out for one spot in India's five-man attack.
"When you look at the WTC, if I remember from the last time India were in the final, what you learn from that game is very important," Shastri said. "You've got to pick a team that suits the conditions. Last time in Southampton the weather was really overcast. Hence I'll pick my 12.
"And then, depending on the conditions, if four seamers are playing, then it'll be Umesh and Shardul who'll play with Siraj and Shami. But if two spinners are playing, which should be the case at The Oval, seeing what the weather is existing in England at the moment, where it's nice and sunny at times, then it will be Ashwin, Jadeja, Shardul, Shami and Siraj."
India have been training at Arundel Castle over the last week or so, with the coaching staff and a first batch of players starting preparations on May 25. The rest of the team has arrived in groups since then, with the five players involved in the rain-affected IPL final in Ahmedabad, which went into its reserve day - Gill, Shami, Bharat, Jadeja and Rahane - joining their team-mates on June 1.
"We have been debating that," Vettori said in a media interaction prior to Australia's training session in Beckenham. "I think Jadeja will play because of the batting he brings to the table and how successful he has been at that No. 6 position. Then the question will be around that fourth seamer and the allrounder in Thakur and Ashwin, but they are [both] pretty good choices."
Vettori felt the pitch at The Oval would play true to its character despite the unusual timing of the Test match, and bring spinners into play.
"Ashwin is an incredible bowler and he will be first choice in most teams, and just with their combinations it may lead to that [him missing selection]," Vettori said. "We expect The Oval to behave how it always behaves. It is a good wicket, but it can offer a lot to the spinners as the game goes on."