Whatever you say about prioritising domestic cricket (or not), the IPL will be far more important for international selection than the Syed Mushtaq Ali Trophy. And arguably even T20Is, given how little international T20 cricket India have played since this team management was hurriedly given an extension following the ODI World Cup. So this IPL is huge for contenders for places because there isn't even a week between the IPL and the T20 World Cup in the USA and the West Indies.
Let's firstly look at the players that can be considered reasonable certainties. Any such list should always start with Jasprit Bumrah. Then comes the captain, Rohit Sharma. His opening partner is more or less locked in: Yashasvi Jaiswal. And once you bring back Rohit, there is no way you don't bring back Virat Kohli. There is the added selectorial merit of experience and Kohli's efficiency against high pace. The only other batter who can confidently start putting together his paperwork for visas is Suryakumar Yadav.
Kuldeep Yadav has more or less booked his place as the wristspinner, and Ravindra Jadeja is more or less a given as the fingerspinning allrounder. That's seven spots out of 15.
Keeping that in mind, here is what the selectors will be looking at keenly during the IPL.
Spin disrupters
If, for whatever reason, the selectors and the team management have decided to stick with the core of Rohit and Kohli, opposition spinners will fancy them. Even Suryakumar, a much more effective T20 batter, goes considerably slower against spin than against pace. Left-arm spin, especially, becomes an effective defensive tool against India.
To counter exactly this, India have been backing Shivam Dube, who played the exact same role for Chennai Super Kings in last year's IPL. However, there is one big difference: CSK could do it because of the Impact Player rule, which allowed them to use Dube in that super specialist role.
Shubman Gill and Ruturaj Gaikwad have good numbers against spin, but that's because they start against the new ball and are in by the time they face spin in the middle overs.
Seam-bowling allrounder
If fully fit and in form, new Mumbai Indians captain Hardik Pandya is a definite starter. That seems a formality now, but the selectors will want to see what kind of role he plays for his IPL team. The other question for the selectors will be: is the selection of Dube, whom the team management has been trying to give some bowling, independent of Hardik's availability?
Wicketkeeper
Not a specialist position anymore. He is a hitter who can keep wicket. Jitesh Sharma is the closest to sealing that spot, but the decision-makers would ideally have liked to see him a little more against international attacks. If there is a slight doubt around him, it is probably because the BCCI had no coach or captain for the T20 World Cup when the recent set of T20Is began, and the interim team management kept playing Ishan Kishan, which not only deprived a more suitable candidate game time but also gave false hope to Kishan.
One of the great stories of this IPL is going to be the return of Rishabh Pant from the life-threatening accident a year and a quarter ago, but the national selectors might exercise some caution when it comes to rushing him back and that too at a World Cup.
If KL Rahul chooses to bat in the middle order in the IPL and can recreate the effectiveness he displayed for Royal Challengers Bangalore in the middle order in 2016, he can be an interesting option to look at. Especially because he is versatile and can be one back-up batter for more than one role.
Death-overs pace-hitter
Not exactly a separate head count but when they pick players for the aforementioned roles, they will have to consider at least two who can hit high pace in overs 17 to 20. Rinku Singh has been doing that role; there is no pressing reason to keep him out of the 15, but the final XI will be a challenge once everyone is back.
Two more fast bowlers
Bumrah is there for sure, but India need at least two more quicks for the starting XI. At the moment, no one is closer to sealing the place than the other. Ideally, they should be able to hit a six or two, but the selectors are not exactly spoilt for choices. The last squad had Arshdeep Singh, Avesh Khan and Mukesh Kumar. Mohammed Siraj, who was key in the Tests against England, will definitely be back in the mix. If Mohsin Khan, who has had his fitness issues, is bowling for Lucknow Super Giants, he is someone the selectors will want to look at.
Back-ups
You can have four of them. The selectors will have to choose among a fourth fast bowler, another wristspinner in Ravi Bishnoi, a spin-bowling allrounder in Axar Patel, an extra wicketkeeper-hitter who can possibly be batting back-up, a top-order back-up in the mode of Gill, and a pure middle-order hitter.