Whiteside has been a lot better than his detractors have claimed. He has flaws, and his style sometimes makes it look like he's not engaged, but for the most part I don't think that's the case. He leads the team in PER, TS%, all rebounding metrics, winshares/48, Defensive Winshares, & Defensive BPM; and he's 2nd on the team in Offensive Winshares, Offensive BPM, BPM, and Value Over Replacement. He's at career highs in PER, TS%, Offensive BPM, & BPM. And he's Portland's only real rim protector and interior defensive presence. His rebounding is down a little but he's had to be a man alone on the glass, and his teammates are lousy at blocking out.
he's easily been Portland's 2nd best player and Portland looked like shit in the 3 games he missed
on the other hand, I just can't see Portland re-signing him unless he accepts less than 10M/year to be a backup, and even then, the Blazers probably can't afford him (or unless Nurkic has issues coming back). Still, I'd question if Jody Allen would be willing the tax exposure of bringing Whiteside back, but that also means trading him for a longer contract may not be in the plans either. I wouldn't be surprised if Whiteside remains a Blazer all season then walks this summer. Portland may value his expiring contract more than they would any trading alternative