BCCI Introduced Impact Player Rule This year in IPL .
Teams must pick 4 substitutes during the toss, and only one can be an Impact Player. An Indian player must be the Impact Player, except when there are 3 or fewer overseas players in the team, in which case an overseas player can be used. If an overseas player is used as the Impact Player, a 5th overseas player cannot play.
The team captain chooses the Impact Player, who can be introduced before the innings start, after an over, a wicket, or a retiring batter. Replaced players cannot participate further and cannot act as substitute fielders. An Impact Player cannot be a captain.
One Impact Player per team per match is optional. Injured players can be replaced with an Impact Player, but if the Impact Player is injured, a substitute fielder is allowed only if umpires agree. Penalty time applies to substitute players as per playing conditions.
I don't like this rule because it gives one team an extra player on the field, which seems unfair. I think it would be better if teams could choose their players after a coin toss. Maybe they could use the impact player rule only a few times to make the game more interesting.
Right now, teams can keep batting until only one player is left, and it's almost impossible to defend scores below 180. This could be a problem for India's all-rounder players like Jadeja and Pandya, who might not be able to keep up for more than 5 years.
To make the game more interesting, captains can change the role of their best player to focus on specific parts of the game, like the first six overs or the last few overs. This means captains need to be really smart about when to use their best player. If the best player can be changed at any time during the game, it takes away some of the advantage of having a really good player.
Although the impact player rule might be fun at first, I don't think it's a good idea in the long run. In white ball cricket, having a player who can both bat and bowl well is very important.
It only undermines the role of the all-rounder if you assume that you can win games with just 5 bowlers. Most of the best T20 teams have at least a 6th bowling option and some have more than that. However, teams aren't picking 6 bowlers who can't bat and then subbing one of them out for a batsman because that would still leave them with a very long tail. Therefore, all-rounders are still important and if you don't believe me, just look at the IPL auction and which players are going for the biggest money - Stokes, Curran, Green, etc.
In my opinion, it might be a good thing because it gives an advantage to the side bowling second to assess the conditions and bring in a bowler to suit those conditions. Too often, T20 games are won on the toss of the coin by the side that chases. We'll have to wait and get a bit more data to see if my theory is correct!