Would force team to either move on from Chandler or Len
The Suns are likely going to move on from either Tyson Chandler or Alex Len regardless, and potentially other higher contract players as well. If Tyson Chandler is retained, his contract is up in only two years. However, if Alex Len is kept he would probably be re-signed for at least four years if not five meaning that his contract (which will grow larger and larger as each season concludes) will slowly squeeze out space and flexibility under the cap.
Adding Millsap on a shorter contract will pinch short-term flexibility, but will provide a significant cap boost when his contract runs out. If he plays out his contract in Phoenix that would happen a year after Tyson Chandler, but it would be a year quicker than Alex Len – and potentially other free agents that Phoenix could sign this offseason who might demand four years, or five if acquired in a sign and trade.
If Millsap is not signed, and no other large contract is added to the roster, then both Chandler and Len are retained meaning that at least for the time being the frontcourt lineup remains stagnant. Add the potentially large contract of Alan Williams’ contract, and there will definitely be less flexibility overall.