Shastri also lauded the youngsters in the team for their fearless way of playing cricket.
India defeated England in the fourth and final Test by an innings and 25 runs at the Narendra Modi Stadium, will now face New Zealand in the WTC final slated to be played from June 18 to 22.
Sundar scored a brilliant 96* in India’s first innings in the fourth Test in Ahmedabad, helping India make 365 from 146/6 adding century partnerships with Ravichandran Ashwin and Akshar Patel in the process. He was left stranded four runs short of his maiden Test century, as Mohammed Siraj and Ishant Sharma were dismissed by Ben Stokes in five balls.
"Washington Sundar has far more natural ability than I had. I think he should be batting in top-four for his state, there is no question about that. I think he should be batting in the top four, he is good enough and he belongs there.
At the same time, if he can focus on his bowling, India would have a very good number six in the future. Somebody could get you a 60-70 and then bowl for you. That was my role at number six, and I think he can do the same role and even better," said Shastri during a virtual press conference on Sunday.
Shastri also lauded the way youngsters are playing freely, not getting bogged down by the pressure of the situation.
It was unreal, this innings in the fourth Test is even better than Brisbane because you are playing at home and you have a World Championship on the line. 50 adrift from the opposition and you are batting with Pant, yes you have Axar to come in next but your objective is to get closer to 205.
"These youngsters are not thinking of that, they are playing normal and fearless cricket. They are playing free cricket, and then they went on to get 360," he added.
India was accused of poor fielding on their tour of Australia, dropping multiple catches and stumpings, but this series saw a significant improvement in that.
"Fielding coach is outstanding, I do not need to have a word with him. We have been in a bubble for the last five months, we have played eight Tests. In my time, probably you would play these many Tests in a year. In 70 days, they played eight Tests living in a bubble. Oppositions were England and Australia, mental fatigue would be there and you would drop catches.
We were not the only team that dropped catches, Australia dropped as many catches as us, if not more. The fact is when we had to take those catches to win Test matches. We did, that's all I want to remember, nothing else. Our fielding coach (R Sridhar) is the best in the world, understated and he is an Indian, he is one of the best," Shastri added.
India also returned to the top of the ICC Test team rankings and have also ended on no.1 spot in ICC Test Championship table with 72.2 percentage points.
(ANI inputs)