This is how it’s going to work; a team will have to list four substitutes at the toss. They can use any one of them as their Impact Player. Unlike the SMAT, the Impact Player can be brought in anytime. The replaced player will take no further part in the match, not even as a substitute fielder. Only if a team fields three or fewer overseas players in their playing XI, will they be allowed to play an overseas player as an Impact Player.
The IPL committee has also clarified that, ""a delayed start reduces the total amount of overs available to both sides to less than 20 overs per innings prior to the commencement of the match. Impact Player can be utilized at any time during the match."
Expect the demand for all-rounders to go down in the long run, with the rule incentivizing teams to go for specialist batters and bowlers. In some sense, teams that built their squads around all-rounders and batting/bowling depth in the mega auction will feel a bit hard done by.
Moving on, this rule will also encourage players to play more high risk cricket than ever before. Batters can now bat knowing that their team will have the option of bringing in an additional batter, in case of a collapse. Ideally, this should also help teams to look past anchors to fill their top-order slots. But, some baffling strategies of IPL teams in the past means that we will be looking at far from ideal scenarios, more often than not.
Like everything new, expect teams to take a bit of time to adapt to these changes. It’s very likely that most teams will play it safe and look to make the substitution in the second innings, when they have a lot more clarity on variables such as ground conditions and match situations. Bringing an Impact Player as early as the first innings would only mean that the team has messed up in drafting their XI in the first place.