Summary
Green has transitioned to being a small-ball four in recent years, and his role went even further playing as a small-ball five during his last few stops in Houston, Brooklyn, and now Denver, although slightly less so with the Nuggets considering their personnel. In '20-'21. Green gave the Nets some versatility in their options for a closing lineup, as Green can certainly hold his own at center, unless the opposing team has a dominant post big like Nikola Jokic or Joel Embiid, one of which he now plays with.

Green started a majority of the games for Denver in '21-'22, filling in for the injured Michael Porter, Jr. After shooting 42% from three in '20-'21, a career high, Green fell back to 31% in '21-'22. He has reduced his midrange attempts as he has aged and replaced them with more threes, which has helped his efficiency, something he struggled with throughout his career. He has also been helped by spending more time off the ball, with a higher proportion of hit attempts being spot-up jumpers rather than unassisted baskets that he created for himself.

Green is still an effective transition player, and despite being 35 years old he still has some athleticism, and will still break out a poster dunk every once in a while. His shooting numbers at the rim are also very good.

It's probably a toss up at this point whether Green will opt out, since he's been a solid contributor to the Nuggets but he hasn't shot the ball well and has gotten more minutes than he would have if the Nuggets were fully healthy. His age will certainly play a factor in any free agent discussions, as I doubt he would get any long-term deals.
 
Cap Considerations
Green has a $4.5 million player option for 2022-2023, and if he declines that option he will be an unrestricted free agent with an $5.4 million cap hold and Non-Bird Rights. If Green opts for free agency, the Nuggets will be somewhat limited in their means of re-signing him. Since they will only have his Non-Bird Rights, the most they could offer him using the Non-Bird Exception is a contract starting at $5.4 million. This should be enough to re-sign Green, but since the Nuggets will have limited resources to replace Green if he leaves, he may be able to use that as leverage to get the full amount allowed under the Non-Bird Exception.

Other teams will have multiple ways to sign Green as even teams without cap space could use any of the Non-Taxpayer MLE, Taxpayer MLE, or possibly even the Room MLE to sign him.