1. Jusuf Nurkic
Let's just get this out of the way at the top - the Suns would likely trade center Jusuf Nurkic if they could. Despite getting a great regular season out of him - he remained healthy and outplayed Ayton for much of a campaign - the limitations of Nurkic were badly exposed in the playoffs.
They may not be able to move off him this coming season - although with only two years and $37 million left on his current deal he is rapidly becoming an expiring contract - but this is likely going to be the point in which he may come off the bench. That's a best case scenario with Ighodaro, although we haven't even hit free agency yet.
Nurkic can still do a job for this roster - especially on the offensive end - he is streets ahead of any of the three newbies the Suns added in that area. But he's nowhere near mobile or athletic enough to stop big men with any sort of post game or burst around the basket. Bigger centers such as Rudy Gobert and jonas Valanciunas also get the better of him as well.
Alongside the need for a point guard, frontcourt depth was the greatest need for the Suns this offseason. They've addresssed this in spades with their new recruits, and it also means the end of Nurkic's role as he knows it with the Suns as well. There's still a place for him - in part because there has to be - but next season is surely going to look very different for the Bosnian big man.