The Moto Z Play was probably the best of Motorola's first round of modular Z phones. It wasn't the fastest, but it was reasonably priced and got amazing battery life. It was a bit on the chunky side compared to its brethren, but Motorola is reportedly looking to rectify that. However, that means it won't have the same amazing longevity.
Evan Blass over at VentureBeat says the Moto Z2 Play will be a millimeter thinner this year (6mm versus 7mm) and 20g lighter (145g versus 165g). This puts it more in-line with the rest of the Z series. It will also get a small internal boost with a Snapdragon 626, 4GB of RAM, and 64GB of storage. Although, the screen will remain a 5.5-inch 1080p AMOLED.
The trade off for that slimmer frame is a smaller battery. Last year's Moto Z Play had a 3,510mAh battery, but this time it'll apparently be just 3,000mAh. If that's true, it's not going to get the same multi-day battery life as last year's model. It might perform just fine with the modest hardware, but the battery life is what made the Moto Z Play special. The Z2 Play might be just another modular phone.