Apple has seen an over 50% sequential increase in Apple Watch Series 3 sales in the fiscal quarter ended September 30, and some market watchers expect that Apple is likely to add more partners into its upstream supply chain to increase its profitability, while reducing production risk.

Apple Watch's overall shipments are expected to reach at least 25 million units in 2018 and most of the sales will be contributed by first-time buyers instead of replacement demand from users of previous-generation models, the sources estimated.

Upstream players including Quanta Computer, Universal Scientific Industrial (USI), Career Technology, Kinsus Interconnect Technology and E&R Engineering are expected to see increasing orders for the Apple Watch, said the sources adding that the Foxconn Group's affiliate ShunSin Technology has also recently landed orders for providing SiP (system in package) packaging services to Apple Watch and will begin the supply in March 2018.

However, these players declined to comment on their orders or clients.

With ShunSin having entered into the supply chain of the Apple Watch, the market watchers believe that Foxconn may also have interest in obtaining Apple Watch's assembly orders.